镓铟氧化物薄膜的制备及性质研究
|
摘要
近几年来,由于透明氧化物半导体材料在发光二极管、激光器、紫外探测器、透明薄膜晶体管、薄膜太阳能电池及平面显示等方面具有广阔的应用前景,因而引起了人们的广泛关注。In_2O_3和Ga_2O_3是具有直接带隙的透明氧化物半导体材料,带隙宽度分别为3.6eV和4.9eV。In_2O_3作为一种重要的n型半导体材料,特别是锡掺杂的氧化铟(ITO)薄膜,因其优良的光电性能而被广泛应用于太阳能电池及平面显示等领域。ITO及目前大量使用的透明氧化物半导体材料均存在着一个共同的问题,那就是:光学带隙一般小于3.7eV。随着透明光电子学和光电子器件的不断发展,要求氧化物半导体材料的透明区域向紫外扩展。β-Ga_2O_3是一种很有潜力的深紫外透明半导体材料,但是其过高的带隙宽度使得β-Ga_2O_3作为深紫外透明导电薄膜材料存在一定的困难。因此,有必要研究一种新型的可调制带隙宽度的透明半导体薄膜材料。镓铟氧化物(Ga_(2-2x)In_(2x)O_3)材料可以认为是Ga_2O_3和In_2O_3两种材料的合金,其带隙宽度可以通过改变样品中Ga与In的比例,在3.6eV到4.9 eV之间调制,因此是一种很有希望的紫外光电材料。目前,国际国内对Ga_(2-2x)In_(2x)O_3(0.1≤x≤0.9)薄膜材料的研究工作尚缺乏深入系统的研究。通过研究制备不同组分的Ga_(2-2x)In_(2x)O_3薄膜,并对制备薄膜的生长、组分、晶格结构、结构相变、电学和光学性质进行较为系统的研究,将会为该材料在透明电子器件及紫外电子器件上的应用奠定基础。在这样的背景下,本论文开展了镓铟氧化物薄膜的MOCVD法制备及其性质的研究。
本论文分为三大部分。第一部分采用MOCVD法制备了Ga_2O_3薄膜,研究了薄膜的结构及光学性质;第二部分制备出了高质量的In_2O_3单晶薄膜,研究了薄膜的结构、光学及电学性质,并首次观察到α-Al_2O_3衬底上制备的In_2O_3薄膜的带间跃迁光致发光现象;第三部分采用MOCVD法制备了Ga_(2-2x)In_(2x)O_3(0.1≤x≤0.9)薄膜和Sn掺杂的Ga_(1.4)In_(0.6)O_3薄膜,较为系统的研究了薄膜的结构、光学以及电学性质。
第一部分主要的研究工作及结果如下:
采用MOCVD法,以高纯Ga(CH_3)_3作为镓源,高纯O_2作为氧源,高纯N_2作为载气,在600℃衬底温度下成功地在蓝宝石(0001)衬底上制备出了Ga_2O_3薄膜,研究了退火处理对制备薄膜结构和光学性质的影响。XRD与AFM测试结果表明,制备的Ga_2O_3薄膜呈现非晶结构;经退火处理后薄膜结晶程度得到明显改善,由非晶转变为了具有β-Ga_2O_3结构的多晶薄膜;且随着退火温度的升高,薄膜的择优取向性增强,晶粒增大,薄膜结晶质量变好。样品的透射谱测量结果表明,退火前后薄膜在可见光区的透过率均超过95%;退火处理后,薄膜样品在近紫外区的透过率得到显著提高,样品的吸收边向短波长方向略有移动,未退火及800℃退火后样品的光学带隙分别为4.71eV和4.89eV。
第二部分主要的研究工作及结果如下:
采用MOCVD方法,以高纯In(CH_3)_3作为铟源,高纯O_2作为氧源,高纯N_2作为载气,首次成功地在蓝宝石(0001)衬底上制备出了高质量的In_2O_3单晶外延薄膜。对不同衬底温度下制备薄膜的晶格结构、光学和电学性质进行了研究,并对In_2O_3单晶薄膜的外延生长机理进行了分析。XRD测试结果表明,制备薄膜具有氧化铟的立方结构,且具有沿(111)的单一取向。650℃衬底温度下制备的薄膜具有最好的结晶质量。HRXRD和HRTEM测试结果表明在650℃衬底温度下制备的样品为具有立方结构的单晶薄膜,且薄膜与蓝宝石(0001)衬底存在In_2O_3(111)//Al_2O_3(0001),In_2O_3[(?)0]//Al_2O_3[11(?)0]的外延关系。薄膜(222)面的ω摇摆曲线半高宽仅为0.14°,这一结果显示制备样品具有很好的单晶质量。样品的透射谱测量结果表明,不同衬底温度下制备的薄膜在可见光范围的透过率均超过90%;650℃衬底温度下制备薄膜的光学带隙为3.66eV。样品的霍尔测试结果表明,制备In_2O_3薄膜的最低电阻率为5.10×10~(-3)Ω·cm、霍尔迁移率最高达35.2cm~2·v~(-1)·s~(-1),载流子浓度为1.61×10~(19) cm~(-3)-4.38×10~(19) cm~(-3)。
室温下对650℃衬底温度下制备的In_2O_3薄膜进行光致发光测量,首次在337nm附近观测到一个强而尖锐的紫外发光峰。低温测量时,337 nm附近发光峰结构没有出现明显变化,但发光峰的位置出现不同程度蓝移。337 nm附近的紫外发光峰被归因于电子从导带底到价带顶的跃迁。
第三部分主要的研究工作及结果如下:
1.首次采用MOCVD法,以高纯Ga(CH_3)_3作为镓源,高纯In(CH_3)_3作为铟源,在550℃衬底温度下蓝宝石(0001)衬底上制备出了Ga_(2-2x)ln_(2x)O_3(0.1≤x≤0.9)薄膜。对制备薄膜的晶格结构、结构相变、组分、光学和电学性质进行了系统研究,并研究了高温退火处理对生长Ga_(2-2x)In_(2x)O_3薄膜的结构和光电性能的影响。XRD测试结果表明,随着样品中In含量的降低,Ga_(2-2x)In_(2x)O_3薄膜的结构先由立方In_2O_3结构转变为非晶,进而转变为多晶β-Ga_2O_3结构;700℃退火处理后薄膜结构得到明显改善,对于富In及Ga与In比例相同的样品其结晶质量得到了明显的提高,而对于富Ga的样品其择优取向发生明显的改变。对样品的XPS和RBS的分析结果表明,采用MOCVD方法制备的Ga_(2-2x)In_(2x)O_3薄膜的组分与我们的实验初始设定值是一致的。样品的透射谱测量结果表明,制备薄膜样品在可见光区的透过率在扣除了衬底的影响后均达到了85%以上,带隙宽度随样品中Ga含量的改变在3.76 eV到4.43eV之间变化;经过退火处理后,薄膜样品在近紫外区的透过率得到显著提高,样品的带隙宽度明显增大。对薄膜的电学性能测试表明,Ga_(2-2x)In_(2x)O_3薄膜的电阻率随Ga含量的增大由3.414×10~(-3)Ω·cm单调增加到6.71×10~4Ω·cm,且经退火处理后薄膜的电阻率进一步升高。
2.采用MOCVD法,以高纯Ga(CH_3)_3作为镓源,高纯In(CH_3)_3作为铟源,在700℃衬底温度下蓝宝石(0001)衬底上制备出了Ga_(2-2x)In_(2x)O_3(0.1≤x≤0.9)薄膜。对制备薄膜的晶格结构、组分、光学和光致发光性质进行了系统研究。XRD和HRTEM测试结果表明,随着样品中In含量的增加,Ga_(2-2x)In_(2x)O_3薄膜的结构先由多晶β-Ga_2O_3结构转变为立方In_2O_3结构多晶薄膜,进而转变为具有In_2O_3(111)单一择优取向的单晶结构薄膜。样品的透射谱测量结果表明,所有制备样品在可见光区的平均透过率均超过90%,薄膜的带隙宽度随Ga含量的增加从3.72 eV单调增加至4.58eV。
室温下对不同铟组分的薄膜样品进行光致发光测量,对于In含量较高(x≥0.5)的样品,在338 nm(3.67eV)附近观测到了紫外发光峰,并且紫外发光峰的相对强度随In含量的减小而减弱;而当Ga含量较高(0<0.5)时,在332nm(3.73eV)附近观测到一个较为尖锐的紫外发光峰,并且随着Ga含量的增加发光峰的强度增强。对x=0.3的样品进行低温测量时,332 nm附近发光峰的位置出现不同程度蓝移。尝试性地对不同组分Ga_(2-2x)In_(2x)O_3薄膜的光致发光机制进行了分析,338 nm处发光峰的起源被归因于电子从导带到价带的跃迁;332 nm处发光峰可能起源于Ga_(2-2x)In_(2x)O_3中β-Ga_2O_3晶粒导带到受主的跃迁发光。
3.首次采用MOCVD法,以高纯Ga(CH_3)_3作为镓源,高纯In(CH_3)_3作为铟源,高纯Sn(C_2H_5)_4作为锡源,在550℃衬底温度下蓝宝石(0001)衬底上制备出了不同Sn掺杂浓度的Ga_(1.4)In_(0.6)O_3(Ga_(1.4)In_(0.6)O_3:Sn)薄膜,研究了掺杂浓度对薄膜结构和光电性能的影响。对不同掺杂浓度Ga_(1.4)In_(0.6)O_3:Sn薄膜样品的结构性质及形貌分析表明,当掺杂浓度超过3%时,样品由非晶结构转变为具有单斜Ga_2O_3结构的多晶薄膜;并且随着Sn掺杂浓度的增加,Ga_(1.4)In_(0.6)O_3:Sn薄膜的晶粒明显增大,结晶质量得到进一步的改善。样品的透射谱和霍尔测试结果表明,制备Ga_(1.4)In_(0.6)O_3:Sn薄膜的光学带隙、电阻率、载流子浓度和霍尔迁移率均随掺杂浓度不同而发生变化。其中掺杂比例为5%的Ga_(1.4)In_(0.6)O_3:Sn薄膜具有最佳的光电性能,其可见光透过率超过85%,光学带隙为3.85 eV;室温下该样品的电阻率和霍尔迁移率分别达到了4.9×10~(-3)Ω·cm和21.4 cm~2·v~(-1)·s~(-1)。
In recent years, intense interest has been paid to transparent oxide semiconductors (TOSs) owing to their potential applications in light-emitting diodes, laser diodes, ultraviolet (UV) detectors, transparent thin-film transistors, flat panel displays and thin-film solar cells. Both In_2O_3 and Ga_2O_3 are good TOSs with direct band gap energy of 3.6 and 4.9 eV, respectively. In_2O_3 is a very important n-type transparent semiconductor and has been widely used in many fields such as solar cells and flat-panel displays owing to its excellent optoelectrical properties. The optical bandgap of the conventional transparent oxide semiconductors such as ITO films is usually smaller than 3.7eV. A need for materials which are transparent in the UV region has emerged with the development of transparent optoelectronics and optoelectronic devices. Ga_2O_3 with the monoclinic structure (β-Ga_2O_3) is a promising candidate for deep-ultraviolet (UV) transparent conductive oxides. But Ga_2O_3 as a deep-UV transparent conductive material presents some difficulties due to its over high band gap energy. Hence, it is necessary to investigate novel bandgap tunable TOSs materials. (Ga_(2-2x)In_(2x)O_3) is considered to be an alloy of In_2O_3 and Ga_2O_3. The band gap of (Ga_(2-2x)In_(2x)O_3) could be tuned from 3.6eV to 4.9eV by controlling the composition of the films, and this make (Ga_(2-2x)In_(2x)O_3) a promising UV photoelectric material. Until now, there is still lack of systematical investigation for properties of (Ga_(2-2x)In_(2x)O_3) (0.1≤x≤0.9) films. To prepare Ga_(2-2x)In_(2x)O_3 films and investigate the growth mechanism, film composition, crystal structure, phase transition and optoelectrical properties of the films will lift this material to higher potential in the field of transparent and UV optoelectronic devices. Under such background, the preparation and characterization of Ga_(2-2x)In_(2x)O_3 films are investigated in this article.
The content of this article consists of three parts. In the first part, the Ga_2O_3 films were deposited by MOCVD. The structural and optical properties of the films were investigated. In the second part, high quality In_2O_3 films were prepared by MOCVD. The structural, optical and electrical properties of the films were investigated in detail, and the PL phenomena of band-to-band transition in In_2O_3 films prepared onα-Al_2O_3 were first observed. In the third part, Ga_(2-2x)In_(2x)O_3 (0.1≤x≤0.9) and Sn doped Ga_(1.4)In_(0.6)O_3 films were prepared by MOCVD. The structural, optical and electrical properties of the films were investigated systematically.
The major research work and results of the first part are as follows:
The Ga_2O_3 films were successfully prepared onα-Al_2O_3 (0001) substrates at 600℃by MOCVD. Ultra high purity Ga(CH_3)_3, N_2 and O_2 were used as the organometallic source, carrier gas, and oxidant, respectively. The film deposition method was described in this part and the annealing effect on the structural and optical properties of deposited films were investigated. XRD and AFM results indicated that the deposited film was amorphous and transformed to polycrystalline structure ofβ-Ga_2O_3 film after annealing. The increase of the annealing temperature could enhance the preferred orientation, enlarge the grain size and improve the crystallization of the film. The optical transmittance spectra showed that the average transmittance in the visible range for the as-deposited and annealed films was over 95%. The transmittance of the annealed film in the near UV region was obviously improved and the absorption edge shifted to shorter wavelength. The optical gaps for the as-grown and annealed samples were 4.71 eV and 4.89eV, respectively.
The major research work and results of the second part are as follows:
1. High-quality In_2O_3 epitaxial films were successfully prepared onα-Al_2O_3 (0001) substrates by MOCVD for the first time. Ultra high purity In(CH_3)_3, N_2 and O_2 were used as the organometallic source, carrier gas, and oxidant, respectively. The structural, optical and electrical properties of the films as a function of substrate temperature were investigated, and the epitaxial growth mechanism of single crystalline In_2O_3 films was analyzed. The XRD results indicated that the prepared samples are pure In_2O_3 films of body-centered cubic (bcc) structure with a single orientation of (111) direction. The sample prepared at 650℃substrate temperature has the best crystalline quality. HRXRD and HRTEM results indicated that the sample was single crystalline film having the bcc structure of pure In_2O_3 with a clear epitaxial relationship of In_2O_3 (111)//A1_2O_3 (0001) with In_2O_3 [(?)0]//Al_2O_3[11(?)0]. The fullwidth at half maximum of the to-rocking curve of (222) reflection is only 0.14°, indicating a high quality crystalline structure. The optical transmittance spectra showed that the average transmittance in the visible range for all films was over 90%. The optical band gap for the 650℃prepared sample was 3.66eV. The Hall measurements indicated that the lowest resistivity and the highest Hall mobility for the obtained films were 5.10×10~(-3)Ω·cm and 35.2 cm~2·v~(-1)·s~(-1), respectively. The carrier concentration varied between 1.61×10~(19) cm~(-3) and 4.38×10~(19) cm~(-3).
The PL spectra of the In_2O_3 film deposited at 650℃on sapphire (0001) were measured. An intense and sharp UV PL peak near 337 nm was observed at room temperature for the first time. While measured at low temperature, there were no obvious change for the structure of this UV PL peak, but the peak position shifted towards higher energy. The origin of the UV PL peak near 337 nm was ascribed to the electron transition from the conduction band to the valence band.
The major research work and results of the third part are as follows:
1. The Ga_(2-2x)ln_(2x)O_3(0.1≤x≤0.9) films were prepared onα-Al_2O_3 (0001) substrates at 550℃by MOCVD for the first time. High purity Ga(CH_3)_3 and In(CH_3)_3 were used as the organometallic sources. The crystal structures, structural phase transitions, optical and electrical properties as well as compositions of these films were investigated in detail. In addition, the annealing effect on the structural and optical properties of deposited films was discussed. The XRD results indicated that, as the In content decreases, the structure of the films changed from bcc to amorphous, and finally to monoclinic structure ofβ-Ga_2O_3. After annealing at 700℃, the crystalline quality of all the films was improved and the preferred orientation for the Ga-rich film changed obviously. The compositions of Ga_(2-2x)In_(2x)O_3 films calculated from the XPS and RBS spectra were consist with the experiment enactment values. The optical transmittance spectra showed that the average transmittance in the visible range for all prepared films was over 85%. The Eg of the Ga_(2-2x)In_(2x)O_3 films could be tuned from 3.76 eV to 4.43eV by controlling the Ga content. The transmittance of the films in the near UV region was obviously improved and the band gap energy increased after annealing at 700℃. The resistivity of Ga_(2-2x)In_(2x)O_3 films increased monotonously from 3.414×10~(-3)Ω·cm to 6.71×10~4Ω·cm and increased further after the annealing treatment.
2. The Ga_(2-2x)In_(2x)O_3(0.1≤x≤0.9) films were prepared onα-Al_2O_3 (0001) substrates at 700℃by MOCVD. High purity Ga(CH_3)_3 and In(CH_3)_3 were used as the organometallic sources. The structural, optical and PL properties as well as compositions of these films were investigated in detail. XRD and HRTEM results indicated that, as the In content increases, the films changed from monoclinic structure ofβ-Ga_2O_3 to bcc structure of polycrystalline In_2O_3, and finally to single crystalline In_2O_3 films with a single orientation of (111) direction. The optical transmittance spectra showed that the average transmittance in the visible range for all prepared films was over 90%, and the band gap of the Ga_(2-2x)In_(2x)O_3 films was tuned from 3.72 eV to 4.58eV by controlling the Ga content.
The PL spectra of the Ga_(2-2x)In_(2x)O_3 films were measured at room temperature. For the higher In content (x≥0.5), an UV PL peak near 338nm (3.67eV) was observed. As decreasing the In content, the relative intensity of the UV emission decreased. And for the lower In content (x<0.5), only a sharp UV PL peak located at 332nm (3.73eV) was observed, and the relative intensity of the peak increased with decreasing the In content. For x=0.3, while measured at low temperature, the peak position shifted towards higher energy. The UV PL mechanisms of Ga_(2-2x)In_(2x)O_3 thin films were discussed. The origin of the UV PL peak near 338 nm was ascribed to the electron transition from the conduction band to the valence band. The peak near 332nm was originated fromβ-Ga_2O_3 grains, and the PL mechanisms can be attributed to the electron transition from the conduction band to the acceptor level.
3. Sn-doped Ga_(1.4)In_(0.6)O_3 films were prepared onα-Al_2O_3 (0001) substrates at 550℃by MOCVD for the first time. High purity Ga(CH_3)_3, In(CH_3)_3 and Sn(C_2H_5)_4 were used as the organometallic sources. The structural, optical and electrical properties of the films dependent on doping level were investigated in detail. The structural and morphological analysis revealed that, when the Sn-doping level exceeded 3%, the films changed from amorphous structure to polycrystalline ofβ-Ga_2O_3. The grain size of the films increased obviously on elevating the Sn concentration, which indicated an improvement of crystallization. The optical transmittance spectra and Hall measurements indicated that the optical band gap, resistivity, carrier concentration and Hall mobility for the films changed with the doping level. The 5% Sn-doped Ga_(1.4)In_(0.6)O_3 film exhibited the best optical and electrical properties with average transmittance over 85% in the visible range and optical band gap of 3.85 eV. The resistivity and Hall mobility for the 5% Sn-doped film were 4.9×10~(-3)Ω·cm and 21.4 cm~2·v~(-1)·s~(-1), respectively.
本论文分为三大部分。第一部分采用MOCVD法制备了Ga_2O_3薄膜,研究了薄膜的结构及光学性质;第二部分制备出了高质量的In_2O_3单晶薄膜,研究了薄膜的结构、光学及电学性质,并首次观察到α-Al_2O_3衬底上制备的In_2O_3薄膜的带间跃迁光致发光现象;第三部分采用MOCVD法制备了Ga_(2-2x)In_(2x)O_3(0.1≤x≤0.9)薄膜和Sn掺杂的Ga_(1.4)In_(0.6)O_3薄膜,较为系统的研究了薄膜的结构、光学以及电学性质。
第一部分主要的研究工作及结果如下:
采用MOCVD法,以高纯Ga(CH_3)_3作为镓源,高纯O_2作为氧源,高纯N_2作为载气,在600℃衬底温度下成功地在蓝宝石(0001)衬底上制备出了Ga_2O_3薄膜,研究了退火处理对制备薄膜结构和光学性质的影响。XRD与AFM测试结果表明,制备的Ga_2O_3薄膜呈现非晶结构;经退火处理后薄膜结晶程度得到明显改善,由非晶转变为了具有β-Ga_2O_3结构的多晶薄膜;且随着退火温度的升高,薄膜的择优取向性增强,晶粒增大,薄膜结晶质量变好。样品的透射谱测量结果表明,退火前后薄膜在可见光区的透过率均超过95%;退火处理后,薄膜样品在近紫外区的透过率得到显著提高,样品的吸收边向短波长方向略有移动,未退火及800℃退火后样品的光学带隙分别为4.71eV和4.89eV。
第二部分主要的研究工作及结果如下:
采用MOCVD方法,以高纯In(CH_3)_3作为铟源,高纯O_2作为氧源,高纯N_2作为载气,首次成功地在蓝宝石(0001)衬底上制备出了高质量的In_2O_3单晶外延薄膜。对不同衬底温度下制备薄膜的晶格结构、光学和电学性质进行了研究,并对In_2O_3单晶薄膜的外延生长机理进行了分析。XRD测试结果表明,制备薄膜具有氧化铟的立方结构,且具有沿(111)的单一取向。650℃衬底温度下制备的薄膜具有最好的结晶质量。HRXRD和HRTEM测试结果表明在650℃衬底温度下制备的样品为具有立方结构的单晶薄膜,且薄膜与蓝宝石(0001)衬底存在In_2O_3(111)//Al_2O_3(0001),In_2O_3[(?)0]//Al_2O_3[11(?)0]的外延关系。薄膜(222)面的ω摇摆曲线半高宽仅为0.14°,这一结果显示制备样品具有很好的单晶质量。样品的透射谱测量结果表明,不同衬底温度下制备的薄膜在可见光范围的透过率均超过90%;650℃衬底温度下制备薄膜的光学带隙为3.66eV。样品的霍尔测试结果表明,制备In_2O_3薄膜的最低电阻率为5.10×10~(-3)Ω·cm、霍尔迁移率最高达35.2cm~2·v~(-1)·s~(-1),载流子浓度为1.61×10~(19) cm~(-3)-4.38×10~(19) cm~(-3)。
室温下对650℃衬底温度下制备的In_2O_3薄膜进行光致发光测量,首次在337nm附近观测到一个强而尖锐的紫外发光峰。低温测量时,337 nm附近发光峰结构没有出现明显变化,但发光峰的位置出现不同程度蓝移。337 nm附近的紫外发光峰被归因于电子从导带底到价带顶的跃迁。
第三部分主要的研究工作及结果如下:
1.首次采用MOCVD法,以高纯Ga(CH_3)_3作为镓源,高纯In(CH_3)_3作为铟源,在550℃衬底温度下蓝宝石(0001)衬底上制备出了Ga_(2-2x)ln_(2x)O_3(0.1≤x≤0.9)薄膜。对制备薄膜的晶格结构、结构相变、组分、光学和电学性质进行了系统研究,并研究了高温退火处理对生长Ga_(2-2x)In_(2x)O_3薄膜的结构和光电性能的影响。XRD测试结果表明,随着样品中In含量的降低,Ga_(2-2x)In_(2x)O_3薄膜的结构先由立方In_2O_3结构转变为非晶,进而转变为多晶β-Ga_2O_3结构;700℃退火处理后薄膜结构得到明显改善,对于富In及Ga与In比例相同的样品其结晶质量得到了明显的提高,而对于富Ga的样品其择优取向发生明显的改变。对样品的XPS和RBS的分析结果表明,采用MOCVD方法制备的Ga_(2-2x)In_(2x)O_3薄膜的组分与我们的实验初始设定值是一致的。样品的透射谱测量结果表明,制备薄膜样品在可见光区的透过率在扣除了衬底的影响后均达到了85%以上,带隙宽度随样品中Ga含量的改变在3.76 eV到4.43eV之间变化;经过退火处理后,薄膜样品在近紫外区的透过率得到显著提高,样品的带隙宽度明显增大。对薄膜的电学性能测试表明,Ga_(2-2x)In_(2x)O_3薄膜的电阻率随Ga含量的增大由3.414×10~(-3)Ω·cm单调增加到6.71×10~4Ω·cm,且经退火处理后薄膜的电阻率进一步升高。
2.采用MOCVD法,以高纯Ga(CH_3)_3作为镓源,高纯In(CH_3)_3作为铟源,在700℃衬底温度下蓝宝石(0001)衬底上制备出了Ga_(2-2x)In_(2x)O_3(0.1≤x≤0.9)薄膜。对制备薄膜的晶格结构、组分、光学和光致发光性质进行了系统研究。XRD和HRTEM测试结果表明,随着样品中In含量的增加,Ga_(2-2x)In_(2x)O_3薄膜的结构先由多晶β-Ga_2O_3结构转变为立方In_2O_3结构多晶薄膜,进而转变为具有In_2O_3(111)单一择优取向的单晶结构薄膜。样品的透射谱测量结果表明,所有制备样品在可见光区的平均透过率均超过90%,薄膜的带隙宽度随Ga含量的增加从3.72 eV单调增加至4.58eV。
室温下对不同铟组分的薄膜样品进行光致发光测量,对于In含量较高(x≥0.5)的样品,在338 nm(3.67eV)附近观测到了紫外发光峰,并且紫外发光峰的相对强度随In含量的减小而减弱;而当Ga含量较高(0<0.5)时,在332nm(3.73eV)附近观测到一个较为尖锐的紫外发光峰,并且随着Ga含量的增加发光峰的强度增强。对x=0.3的样品进行低温测量时,332 nm附近发光峰的位置出现不同程度蓝移。尝试性地对不同组分Ga_(2-2x)In_(2x)O_3薄膜的光致发光机制进行了分析,338 nm处发光峰的起源被归因于电子从导带到价带的跃迁;332 nm处发光峰可能起源于Ga_(2-2x)In_(2x)O_3中β-Ga_2O_3晶粒导带到受主的跃迁发光。
3.首次采用MOCVD法,以高纯Ga(CH_3)_3作为镓源,高纯In(CH_3)_3作为铟源,高纯Sn(C_2H_5)_4作为锡源,在550℃衬底温度下蓝宝石(0001)衬底上制备出了不同Sn掺杂浓度的Ga_(1.4)In_(0.6)O_3(Ga_(1.4)In_(0.6)O_3:Sn)薄膜,研究了掺杂浓度对薄膜结构和光电性能的影响。对不同掺杂浓度Ga_(1.4)In_(0.6)O_3:Sn薄膜样品的结构性质及形貌分析表明,当掺杂浓度超过3%时,样品由非晶结构转变为具有单斜Ga_2O_3结构的多晶薄膜;并且随着Sn掺杂浓度的增加,Ga_(1.4)In_(0.6)O_3:Sn薄膜的晶粒明显增大,结晶质量得到进一步的改善。样品的透射谱和霍尔测试结果表明,制备Ga_(1.4)In_(0.6)O_3:Sn薄膜的光学带隙、电阻率、载流子浓度和霍尔迁移率均随掺杂浓度不同而发生变化。其中掺杂比例为5%的Ga_(1.4)In_(0.6)O_3:Sn薄膜具有最佳的光电性能,其可见光透过率超过85%,光学带隙为3.85 eV;室温下该样品的电阻率和霍尔迁移率分别达到了4.9×10~(-3)Ω·cm和21.4 cm~2·v~(-1)·s~(-1)。
In recent years, intense interest has been paid to transparent oxide semiconductors (TOSs) owing to their potential applications in light-emitting diodes, laser diodes, ultraviolet (UV) detectors, transparent thin-film transistors, flat panel displays and thin-film solar cells. Both In_2O_3 and Ga_2O_3 are good TOSs with direct band gap energy of 3.6 and 4.9 eV, respectively. In_2O_3 is a very important n-type transparent semiconductor and has been widely used in many fields such as solar cells and flat-panel displays owing to its excellent optoelectrical properties. The optical bandgap of the conventional transparent oxide semiconductors such as ITO films is usually smaller than 3.7eV. A need for materials which are transparent in the UV region has emerged with the development of transparent optoelectronics and optoelectronic devices. Ga_2O_3 with the monoclinic structure (β-Ga_2O_3) is a promising candidate for deep-ultraviolet (UV) transparent conductive oxides. But Ga_2O_3 as a deep-UV transparent conductive material presents some difficulties due to its over high band gap energy. Hence, it is necessary to investigate novel bandgap tunable TOSs materials. (Ga_(2-2x)In_(2x)O_3) is considered to be an alloy of In_2O_3 and Ga_2O_3. The band gap of (Ga_(2-2x)In_(2x)O_3) could be tuned from 3.6eV to 4.9eV by controlling the composition of the films, and this make (Ga_(2-2x)In_(2x)O_3) a promising UV photoelectric material. Until now, there is still lack of systematical investigation for properties of (Ga_(2-2x)In_(2x)O_3) (0.1≤x≤0.9) films. To prepare Ga_(2-2x)In_(2x)O_3 films and investigate the growth mechanism, film composition, crystal structure, phase transition and optoelectrical properties of the films will lift this material to higher potential in the field of transparent and UV optoelectronic devices. Under such background, the preparation and characterization of Ga_(2-2x)In_(2x)O_3 films are investigated in this article.
The content of this article consists of three parts. In the first part, the Ga_2O_3 films were deposited by MOCVD. The structural and optical properties of the films were investigated. In the second part, high quality In_2O_3 films were prepared by MOCVD. The structural, optical and electrical properties of the films were investigated in detail, and the PL phenomena of band-to-band transition in In_2O_3 films prepared onα-Al_2O_3 were first observed. In the third part, Ga_(2-2x)In_(2x)O_3 (0.1≤x≤0.9) and Sn doped Ga_(1.4)In_(0.6)O_3 films were prepared by MOCVD. The structural, optical and electrical properties of the films were investigated systematically.
The major research work and results of the first part are as follows:
The Ga_2O_3 films were successfully prepared onα-Al_2O_3 (0001) substrates at 600℃by MOCVD. Ultra high purity Ga(CH_3)_3, N_2 and O_2 were used as the organometallic source, carrier gas, and oxidant, respectively. The film deposition method was described in this part and the annealing effect on the structural and optical properties of deposited films were investigated. XRD and AFM results indicated that the deposited film was amorphous and transformed to polycrystalline structure ofβ-Ga_2O_3 film after annealing. The increase of the annealing temperature could enhance the preferred orientation, enlarge the grain size and improve the crystallization of the film. The optical transmittance spectra showed that the average transmittance in the visible range for the as-deposited and annealed films was over 95%. The transmittance of the annealed film in the near UV region was obviously improved and the absorption edge shifted to shorter wavelength. The optical gaps for the as-grown and annealed samples were 4.71 eV and 4.89eV, respectively.
The major research work and results of the second part are as follows:
1. High-quality In_2O_3 epitaxial films were successfully prepared onα-Al_2O_3 (0001) substrates by MOCVD for the first time. Ultra high purity In(CH_3)_3, N_2 and O_2 were used as the organometallic source, carrier gas, and oxidant, respectively. The structural, optical and electrical properties of the films as a function of substrate temperature were investigated, and the epitaxial growth mechanism of single crystalline In_2O_3 films was analyzed. The XRD results indicated that the prepared samples are pure In_2O_3 films of body-centered cubic (bcc) structure with a single orientation of (111) direction. The sample prepared at 650℃substrate temperature has the best crystalline quality. HRXRD and HRTEM results indicated that the sample was single crystalline film having the bcc structure of pure In_2O_3 with a clear epitaxial relationship of In_2O_3 (111)//A1_2O_3 (0001) with In_2O_3 [(?)0]//Al_2O_3[11(?)0]. The fullwidth at half maximum of the to-rocking curve of (222) reflection is only 0.14°, indicating a high quality crystalline structure. The optical transmittance spectra showed that the average transmittance in the visible range for all films was over 90%. The optical band gap for the 650℃prepared sample was 3.66eV. The Hall measurements indicated that the lowest resistivity and the highest Hall mobility for the obtained films were 5.10×10~(-3)Ω·cm and 35.2 cm~2·v~(-1)·s~(-1), respectively. The carrier concentration varied between 1.61×10~(19) cm~(-3) and 4.38×10~(19) cm~(-3).
The PL spectra of the In_2O_3 film deposited at 650℃on sapphire (0001) were measured. An intense and sharp UV PL peak near 337 nm was observed at room temperature for the first time. While measured at low temperature, there were no obvious change for the structure of this UV PL peak, but the peak position shifted towards higher energy. The origin of the UV PL peak near 337 nm was ascribed to the electron transition from the conduction band to the valence band.
The major research work and results of the third part are as follows:
1. The Ga_(2-2x)ln_(2x)O_3(0.1≤x≤0.9) films were prepared onα-Al_2O_3 (0001) substrates at 550℃by MOCVD for the first time. High purity Ga(CH_3)_3 and In(CH_3)_3 were used as the organometallic sources. The crystal structures, structural phase transitions, optical and electrical properties as well as compositions of these films were investigated in detail. In addition, the annealing effect on the structural and optical properties of deposited films was discussed. The XRD results indicated that, as the In content decreases, the structure of the films changed from bcc to amorphous, and finally to monoclinic structure ofβ-Ga_2O_3. After annealing at 700℃, the crystalline quality of all the films was improved and the preferred orientation for the Ga-rich film changed obviously. The compositions of Ga_(2-2x)In_(2x)O_3 films calculated from the XPS and RBS spectra were consist with the experiment enactment values. The optical transmittance spectra showed that the average transmittance in the visible range for all prepared films was over 85%. The Eg of the Ga_(2-2x)In_(2x)O_3 films could be tuned from 3.76 eV to 4.43eV by controlling the Ga content. The transmittance of the films in the near UV region was obviously improved and the band gap energy increased after annealing at 700℃. The resistivity of Ga_(2-2x)In_(2x)O_3 films increased monotonously from 3.414×10~(-3)Ω·cm to 6.71×10~4Ω·cm and increased further after the annealing treatment.
2. The Ga_(2-2x)In_(2x)O_3(0.1≤x≤0.9) films were prepared onα-Al_2O_3 (0001) substrates at 700℃by MOCVD. High purity Ga(CH_3)_3 and In(CH_3)_3 were used as the organometallic sources. The structural, optical and PL properties as well as compositions of these films were investigated in detail. XRD and HRTEM results indicated that, as the In content increases, the films changed from monoclinic structure ofβ-Ga_2O_3 to bcc structure of polycrystalline In_2O_3, and finally to single crystalline In_2O_3 films with a single orientation of (111) direction. The optical transmittance spectra showed that the average transmittance in the visible range for all prepared films was over 90%, and the band gap of the Ga_(2-2x)In_(2x)O_3 films was tuned from 3.72 eV to 4.58eV by controlling the Ga content.
The PL spectra of the Ga_(2-2x)In_(2x)O_3 films were measured at room temperature. For the higher In content (x≥0.5), an UV PL peak near 338nm (3.67eV) was observed. As decreasing the In content, the relative intensity of the UV emission decreased. And for the lower In content (x<0.5), only a sharp UV PL peak located at 332nm (3.73eV) was observed, and the relative intensity of the peak increased with decreasing the In content. For x=0.3, while measured at low temperature, the peak position shifted towards higher energy. The UV PL mechanisms of Ga_(2-2x)In_(2x)O_3 thin films were discussed. The origin of the UV PL peak near 338 nm was ascribed to the electron transition from the conduction band to the valence band. The peak near 332nm was originated fromβ-Ga_2O_3 grains, and the PL mechanisms can be attributed to the electron transition from the conduction band to the acceptor level.
3. Sn-doped Ga_(1.4)In_(0.6)O_3 films were prepared onα-Al_2O_3 (0001) substrates at 550℃by MOCVD for the first time. High purity Ga(CH_3)_3, In(CH_3)_3 and Sn(C_2H_5)_4 were used as the organometallic sources. The structural, optical and electrical properties of the films dependent on doping level were investigated in detail. The structural and morphological analysis revealed that, when the Sn-doping level exceeded 3%, the films changed from amorphous structure to polycrystalline ofβ-Ga_2O_3. The grain size of the films increased obviously on elevating the Sn concentration, which indicated an improvement of crystallization. The optical transmittance spectra and Hall measurements indicated that the optical band gap, resistivity, carrier concentration and Hall mobility for the films changed with the doping level. The 5% Sn-doped Ga_(1.4)In_(0.6)O_3 film exhibited the best optical and electrical properties with average transmittance over 85% in the visible range and optical band gap of 3.85 eV. The resistivity and Hall mobility for the 5% Sn-doped film were 4.9×10~(-3)Ω·cm and 21.4 cm~2·v~(-1)·s~(-1), respectively.
引文
[1] H. Ohta and H.Hosono, Materialstoday June 2004, P 42-51
[2] Nakamura S, Science, 281 (1998) 956
[3] X. L. Chen, Y. G. Cao et al, Growth 209 (2000) 208
[4] G Popovici, G. Xu et al., J. Appl. Phys. 82 (1997) 4020
[5] C. J. Youn, T. S. Jeong et al., J. Cryst. Growth 250 (2003) 331
[6] M. A. Sanchez-Garcia, J. L. Pau et al., Mater. Sci. Eng. B 93 (2002) 189
[7] A. P. Zhang, F. Ren, T. J. Anderson et al., Crit. Rev. Solid State 27 (2002) 1
[8] V. Adivarahan, W.H. Sun, A. Chitnis, et al., Appl. Phys. Lett. 85 (2004) 12.
[9] Y. Taniyasu, M. Kasu, T. Makimoto, Nature 441 (2006) 325.
[10] J. Zhang, X. Hu, A. Lunev, et al., Jpn. J. Appl. Phys. 44 (2005) 7250
[11] J. Mei, F.A. Ponce et al., Appl. Phys. Lett. 90 (2007) 221909
[12] M. Imura, K. Nakano et al., Appl. Phys. Lett. 89 (2006) 221901
[13] Ryo Kajitani et al., Materials Science and Engineering B 139 (2007) 186
[14]T.Y Lin, G.M. Chen, D.Y. Lyu, Solid State Communications 142 (2007) 237
[15] D. M. Bagnall et al., Appl. Phys. Lett. 70 (17) (1997) 2230
[16] Y. Segawa et al., Phys. Stat. Sol. (b) 202 (1997) 202
[17] D. C. Reynolds et al., Solid State Communication, 99 (12) (1996) 873
[18] J. Zhang, Z.G. Liu, C.K. Lin, J. Lin, J. Cryst. Growth 206 (205) 99
[19] F. Zhu, Z. X. Yang, W. M. Zhou, Y. F. Zhang, Physica E, 33(2006) 151
[20] J. Zhang, F. H. Jiang, Chem. Phys. 289 (2003) 243
[21] B. Y. Geng, L. D. Zhang, G W. Meng, T. Xie, X. S. Peng, Y. Lin, J. Cryst. Growth 259 (2003) 291
[22] X. C. Wu, W. H. Song, B. Zhao, Y. P. Sun, Chem. Phys. Lett. 349 (2001) 210
[23] A. F. Pasquevich, M. Uhrmacher, L. Ziegeler, K. P. Lieb, Phys. Rev. B. 48 (1993) 10052
[24] K. Matsuzaki, H. Hidenori et al., Thin Solid Films 496 (2006) 37
[25] M. Orita, H. Hiramatsu, H. Ohta, M. Hirano, H. Hosono, Thin Solid Films 411(2002) 134
[26] Z. Hajnal, J. Miro et al., J. Appl. Phys. 86 (1999) 3792
[27] T. Minami, Shirai, T. Nakatani, Jpn. J. Appl. Phys. 39 (2000) L524
[28] M. Fleischer, H. Meixner, J. Appl. Phys. 74 (1993) 300
[29] T. Miyata, T. Nakatani, T. Minami, J. Lumin. 87-89 (2000) 1183
[30] L. Binet, D. Gourier, J. Phys. Chem. Solids 59 (1998) 1241
[31] G Gundiah, A. Govindaraj, C.N.R. Rao, Chem. Phys. Lett. 351 (2002) 189
[32] J. Zhang, F.H. Jiang, Chem. Phys. 289 (2003) 243
[33] M. Fleischer, H. Meixner, Sensor Actuat. B. 4 (1991) 437
[34] C. Baban, Y. Toyoda, M. Ogita, Thin Solid Films, 484 (2005) 369
[35] Y. X. Li, A. Trinchi et al., Sensor Actuat. B. 93 (2003) 431
[36] P. Sandvik, K. Mi, F. Shahedipour et al., J. Cryst. Growth 231 (2001) 366
[37] C. Sungryong, L. Jongwon et al., Mater. Lett. 57 (2002) 1004
[38] D. Stodilka, A.H. Kitai, Z. Huang et al., SID 00 DIGEST (2000) 11
[39] T. Minami, Y. Kubota, T. Miyata, H. Yamada, SID 98 DIGEST (1998) 953
[40] E. Savarimuthua, K.C. Lalithambikad et al., J. Phys. Chem. Solids 68 (2007) 1380
[41] W.S. Seo, H.H. Jo, K. Lee, J.T. Park, Adv. Mater. 15 (2003) 795
[42] E. Burstein, Phys. Rev. 93 (1954) 632
[43] J.C. Fan and J.B. Goodenough, J. Appl. Phys. 48 (1977) 3524
[44] 李家亮,姜洪义,牛金叶等,现代技术陶瓷107(2006)19
[45] J. Strumpfel* and C. May, Vacuum 59 (2000) 500
[46] J. George and C.S. Menon, Surf. Coat. Tech. 132 (2000) 45
[47] M.J. Alam and D.C. Cameron, Thin Solid Films 377 (2000) 455
[48] C.G. Granqvist and A. Hultaker, Thin Solid Films 411 (2002) 1
[49] A. Rogozin, N. Shevchenko, M. Vinnichenko et al., Appl. Phys. Lett. 85(1) (2004) 212
[50] W.F. Wu and B.S. Chiou, Appl. Surf. Sci. 68(4) (1993) 497
[51] I. Baia, M. Quintela, L. Mendes et al., Thin Solid Films 337(1-2) (1999) 171
[52] H. Ohta, M. Hirano et al., Appl. Phys. Lett. 76 (2000) 2740
[53] H. Kim, J.S. Horwitz, G.P. Kushto et al., Appl. Phys. Lett. 78 (2001) 1050
[54] M. F. A. M. van Hest, M.S. Dabney, J.D. Perkins et al., Appl. Phys. Lett. 87 (2005)032111
[55] R.K. Grupta, K. Ghosh, R. Patel, P.K. Kahol, J. Cryst. Growth 310 (2001) 4336
[56] J. Tamaki, C. Naruo, Y. Yamamoto, M. Matsuoka, Sensor Actuat. B:Chem. 83 (2002) 190
[57] P. Bogdanov, M. Lvanovskaya et al., Sensor Actuat. B:Chem. 57 (1999) 153
[58] V. Romanovskaya, M. Lvanovskaya, P. Bogdanov, Sensor Actuat. B:Chem. 56 (1999)31
[59] Akiyoshi Hattori, Hirokazu Tachibana et al., Sensor Actuat. A:Phys. 77 (1999) 120
[60] Hiroyuki Yamaura, Koji Moriya et al., Sensor Actuat. B:Chem. 65 (2000) 39
[61] Y.F. Zhang, J.Y. Li et al., Scripta Mater. 56 (2007) 409
[62] C.H. Liang, GW. Meng, Y. Lei et al., Adv. Mater. 13 (2001) 1330
[63] G. A. Rozgonyi, and W. J. Polito, Appl. Phys. Lett. 8 (1966) 220
[64] G L. Dybwad, J. Appl. Phys. 42 (1971) 5192
[65] T. Mitsuyu, S. Ono, and K. Wasa, J. Appl. Phys. 51 (1980) 2464
[66] C. Baban, Y. Toyoda, M. Ogita, Thin Solid Films, 484 (2005) 369
[67] Naoki Ohashi, Tsuyoshi Oginoa et al., J. Cryst. Growth 206 (2005) 99
[68] S. Kaleemulla, A. Sivasankar Reddy, S. Uthanna, Mater. Lett. 61 (2007)4309
[69] P. Nath and R. F. Bunshah, Thin Solid Films 69 (1980) 63
[70] K. F. Huang, T. M. Uen, Y.S. Gou et al., Thin Solid Films 148 (1987) 7
[71] H. U. Habermeier, Thin Solid Films 80 (1981) 157
[72] H. Ohta, M. Orita, M. Hirano et al., Appl. Phys. Lett. 76 (2000) 2740
[73] F. O. Adurodija, H. Izumi, T. Ishihara et al., J. Appl. Phys. 88 (2000) 4175
[74] H. Izumi, F.O. Adurodija, T. Kaneyoshi et al., J. Appl. Phys. 91 (2002) 1213
[75] K. Matsuzaki, H. Hiramatsu, K. Nomura et al., Thin Solid Films 496 (2006) 37
[76] J. R. Arthur and J. J. LePore, J. Vac. Sci. & Tecnnol. 6 (1969) 545
[77] M. A. L. Johnson, J. D. Brown, N. A. EI-Masry, J. W. Cook Jr., J. F. Schetzina, H. S. Kong, J. A. Edmond, J. Vac. Sci. Technol. B 16 (1998) 1282
[78] T. Oshima, N. Arai, N. Suzuki, Thin Solid Films 516 (2008) 5768
[79] Y. Sawada,C. Kobayashi, S. Seki, Thin Solid Films 409 (2002) 46
[80] Y. Zhang, H. Ago et al., J. Cryst. Growth 264 (2004) 363
[81] H.W. Kim, N.H. Kim, Mater. Sci. Eng. B 110 (2004) 34
[82] Ch.Y. Wang, M. Ali, Th. Kups et al., Sensor Actuat. B. 130 (2008) 589
[83] J. S. Kim, Phys.Stat.Sol. 187, No.2, 569-573 (2001)
[84] D.P. Yu, J.-L. Bubendorff, Solid State Commun. 124 (2002) 417-421
[85]Nam Ho Kim, Appl. Surf. Sci. 242 (2005) 29-34
[86] C.H. Liang, GW. Meng et al., Adv. Mater. 13 (2001) 1330
[87] H. Ohta, K. Nomura, H. Hiramatsu, Solid State Electron. 47 (2003) 2261
[88] D.D. Edwards, P.E. Folkins, T.O. Mason, J. Am. Ceram. Soc. 80 (1997) 253
[89] L. Binet, G Gauthier, C. Vigreux, D. Gourier, J. Phys. Chem. Solids 60 (1999) 1755
[90] R.J. Cava, J.M. Phillips et al., Appl. Phys. Lett. 64 (1994) 2071
[91] J.M. Phillips, J. Kwo et al., Appl. Phys. Lett. 65 (1994) 115
[92] T. Minami, Y. Takeda et al., J. Vac. Sci. Technol. A 15(3) (1997) 958
[93] J. Jeong et al., Solid State Commu. 127 (2003) 595
[94] A. Bourlange, D.J. Payne et al., Appl. Phys. Lett. 92 (2008) 092117
[95] S.Choopun, R.D.Vispute, et al., Appl. Phys. Lett. 80 (2002) 1529
[96] T.Minemoto, T.Negami, et al., Thin Solid Films 372 (2000) 173
[97] D.D. Edwards, T.O. Mason et al., J. Solid State Chem. 150 (2000) 294
[98] R. Hill, J. Phys. C: Solid State Phys. 7 (1974) 521
[1]H.M. Manasevit, Appl. Phys. Lett. 12 (1968) 156
[2]杨树人,丁墨元,《外延生长技术》,国防工业出版社,1992
[3]杨邦朝,王文生,《薄膜物理与技术》,电子科技大学出版社,1994
[4]H.M. Manasevit, W.I. Simpson, J. Electronchem. Soc. 12 (1968) 156
[5]H.M. Manasevit, J. Cryst. Growth 13 (1972) 306
[6]J. S. Roberts et al., J. Cryst. Growth, 68 (1984) 42
[7]杨于兴,漆璿,《X射线衍射分析》,上海交通大学出版社,1994
[8]左演声,陈文哲,梁伟,《材料现代分析方法》,北京工业大学出版社,2000
[9]C. G. Fonstad, R. H. Rediker, J. Appl. Phys. 42 (1971) 2911
[10]王建祺,《电子能谱学(XPS/XAES/UPS)引论》,国防工业出版社,1992
[1] D. Briggs, M.P. Seah, Practical Surface Analysis, vol. 1, Wiley, New York, 1990, p.609
[2] J.F. Moulder, W.F. Stickle, P.E. Sobol et al., Handbook of X-ray Photoelectron Spectroscopy [M], Minnesota: Physical Electronics, Inc, 1995
[3] V.K. Josepovits, O. Krafcsik, G Kiss, I.V. Perczel, Sensor Actuat. B. 48 (1998)373
[4] F. M. Amanullah, K. J. Pratap, V.H. Babu, Mater. Sci. Eng. B 52 (1998) 93
[5] A. Srinivasan, K. Jagannathan et al., Indian J. Chem. Soc. A18 (1979) 463
[6] X.J. Zhang, H.L. Ma, Q.P. Wang et al., Chinese Phys. Lett. 22 (2005) 995
[1] H. Haitjema, J.J. Ph. Elich, Thin Solid Films, 205 (1991) 93
[2] T. Koida, M. Kondo, Appl. Phys. Lett. 89 (2006) 082104
[3] J.J. Prince, S. Ramamurthy et al, J. Cryst. Growth 240 (2002) 142
[4] J. Striimpfel, C. May, Vacuum 59 (2000) 500
[5] S. Kaleemulla, A.S. Reddy et al., Mater. Lett. 61 (2009) 4309
[6] Ch.Y. Wang, V. Cimalla et al., Thin Solid Films, 130 (2008) 589
[1] Minami T, Takeda Y 1996 J . Vac . Sci. Technol. A . 15 958
[2] J.F. Moulder et al., Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer Corporation, 1979.
[3] W.K. Chu, J.W. Mayer, M.A. Nicolet, Backscattering Spectrometry, Academic,1978, pp. 150
[4] M. Orita, H. Ohta, M. Hirano, and H. Hosono, Appl. Phys. Lett. 77 (2000) 4166
[5] H.D. Xiao, H.L. Ma, C.S. Xue, H. Z. Zhuang, Mater. Chem. Phys. 101 (2007) 99
[6] X.C. Wu, J.M. Hong, Z.J. Han, Y.R. Tao, Chem. Phys. Lett. 373 (2003) 28
[7] J. Zhang, F.H. Jiang, Chem. Phys. 289 (2003) 243
[8] G. Gundiah, A. Govindaraj, C.N.R. Rao, Chem. Phys. Lett. 351 (2002) 189
[9] L. Binet, D. Gourier, J. Phys. Chem. Solids 59 (1998) 1241
[10] V.I. Vasil' tsiv, Ya.M. Zakharko, Ya.I. Prim, Ukr. Fiz. Zh. 33 (1988) 1320
[1] T. Minami, H. Nanto, S. Shooji, S. Takata, Thin Solid Films 111 (1984) 167
[2] E. Burstein, Phys. Rev. 93 (1954) 632
[1] I.Hamberg, C.G. Granqvist, J. Appl. Phys. 60 (1986) R123.
[2] M.Mizuhashi, Thin Solid Films 70 (1980) 91.
[3] B.G Lewis, D.C. Paine, MRS Bull. 25 (2000) 22.
[4] Y. Zhang, H. Ago, J. Liu, M. Yumura, K. Uchida, S. Ohshima, S. Iijima, J. Zhu, X. Zhang, J. Cryst. Growth 264 (2004) 363.
[5] C. Kuo, S. Lu, T. Wei, J. Cryst. Growth 285 (2005) 400.
[6] C. Falcony, J.R. Kirtley, D.J. Dimaria, T.P. Ma, T.C. Chen, J. Appl. Phys. 58 (1985) 3556.
[7] C.G. Granqvist, Appl. Phys., A Mater. Sci. Process. 57 (1993) 19.
[8] J. Lao, J. Huang, D. Wang, Zhifeng Ren, Adv. Mater. 16 (2004) 65.
[9] J. Joseph Prince, S. Ramamurthy, B. Subramanian, C. Sanjeeviraja, M. Jayachandran, J. Cryst. Growth 240 (2002) 142.
[10] J.Q. Hu, F.R. Zhu, J. Zhang, H. Gong, Sens. Actuators B 93 (2003) 175.
[11] T. Koida, M. Kondo, Appl. Phys. Lett. 89 (2006) 082104.
[12] T. Maruyama, K. Fukui, J. Appl. Phys. 70 (1991) 3848.
[13] A. Gurlo, M. Ivanovskaya, A. Pfau, U. Weimar, W. Gopel, Thin Solid Films 307 (1997) 288.
[14] Ch.Y. Wang, V. Cimalla, H. Romanus, Th. Kups, M. Niebelschutz, O. Ambacher, Thin Solid Films 515 (2007) 6611.
[15] W.S. Seo, H.H. Jo, K. Lee, J.T. Park, Adv. Mater. 15 (2003) 795.
[16] L.C. Chen, W.H. Lan, R.M. Lin, H.T. Shen, H.C. Chen, Appl. Surf. Sci. 252 (2006) 8438.
[17] P. Thilakan, J. Kumar, Vacuum 48 (1997) 463.
[1] K. Yanagawa, Y. Ohki, T. Omata, H. Hosono, N. Ueda, H. Kawazoe, Appl. Phys. Lett. 65 (1994) 406.
[2] D.D. Edwards, T.O. Mason, F. Goutenoire, K.R. Poeppelmeier, Appl. Phys. Lett. 70(1997)1706.
[3] A.K. Sharma, J. Narayan, J.F. Muth, C.W. Teng, C. Jin, A. Kvit, R.M. Kolbas, O.W. Holland, Appl. Phys. Lett. 75 (1999) 3327.
[4] T. Minami, Y. Takeda, T. Kakumu, S. Takata, J. Vac. Sci. Technol. A. 15 (1996 )958.
[5] G.B. Palmer, K.R. Poeppelmeier, Solid. State. Sci. 4 (2002) 317.
[6]T. Moriga, M. Mikawa, Y. Sakakibara, Thin Solid Films 4986 (2005) 53.
[7] A. Ohtomo, M. Kawasaki, T. Koida, K. Masubuchi, H. Koinuma, Y. Sakurai, Y. Yoshida, T. Yasuda, Y. Segawa, Appl. Phys. Lett. 72 (1998) 2466.
[8] H. Tanaka, S. Fujita, Appl. Phys. Lett. 86 (2005) 192911.
[9] H. Ohta, M. Orita, M. Hirano, H. Tanji, H. Kawazoe, H. Hosono, Appl. Phys. Lett. 76 (2000) 2740.
[10] J. Joseph Prince, S. Ramamurthy, B. Subramanian, C. Sanjeeviraja, M. Jayachandran, J. Cryst. Growth 240 (2002) 142.
[11] T.J. Courts, D.L. Young, X. Li, MRS Bull. 25 (2000) 58.
[12] N. Ueda, H. Hosono, R. Waseda, H. Kawazoe, Appl. Phys. Lett. 70 (1997) 3561.
[13] M. Orita, H. Ohta, M. Hirano, and H. Hosono, Appl. Phys. Lett. 77 (2000) 4166.
[14] R. Hill, J. Phys. C: Solid State Phys. 7 (1974 )521.
[15] W.K. Chu, J.W. Mayer, Backscattering Spectrometry, Academic, 1978, p. 150.
[2] Nakamura S, Science, 281 (1998) 956
[3] X. L. Chen, Y. G. Cao et al, Growth 209 (2000) 208
[4] G Popovici, G. Xu et al., J. Appl. Phys. 82 (1997) 4020
[5] C. J. Youn, T. S. Jeong et al., J. Cryst. Growth 250 (2003) 331
[6] M. A. Sanchez-Garcia, J. L. Pau et al., Mater. Sci. Eng. B 93 (2002) 189
[7] A. P. Zhang, F. Ren, T. J. Anderson et al., Crit. Rev. Solid State 27 (2002) 1
[8] V. Adivarahan, W.H. Sun, A. Chitnis, et al., Appl. Phys. Lett. 85 (2004) 12.
[9] Y. Taniyasu, M. Kasu, T. Makimoto, Nature 441 (2006) 325.
[10] J. Zhang, X. Hu, A. Lunev, et al., Jpn. J. Appl. Phys. 44 (2005) 7250
[11] J. Mei, F.A. Ponce et al., Appl. Phys. Lett. 90 (2007) 221909
[12] M. Imura, K. Nakano et al., Appl. Phys. Lett. 89 (2006) 221901
[13] Ryo Kajitani et al., Materials Science and Engineering B 139 (2007) 186
[14]T.Y Lin, G.M. Chen, D.Y. Lyu, Solid State Communications 142 (2007) 237
[15] D. M. Bagnall et al., Appl. Phys. Lett. 70 (17) (1997) 2230
[16] Y. Segawa et al., Phys. Stat. Sol. (b) 202 (1997) 202
[17] D. C. Reynolds et al., Solid State Communication, 99 (12) (1996) 873
[18] J. Zhang, Z.G. Liu, C.K. Lin, J. Lin, J. Cryst. Growth 206 (205) 99
[19] F. Zhu, Z. X. Yang, W. M. Zhou, Y. F. Zhang, Physica E, 33(2006) 151
[20] J. Zhang, F. H. Jiang, Chem. Phys. 289 (2003) 243
[21] B. Y. Geng, L. D. Zhang, G W. Meng, T. Xie, X. S. Peng, Y. Lin, J. Cryst. Growth 259 (2003) 291
[22] X. C. Wu, W. H. Song, B. Zhao, Y. P. Sun, Chem. Phys. Lett. 349 (2001) 210
[23] A. F. Pasquevich, M. Uhrmacher, L. Ziegeler, K. P. Lieb, Phys. Rev. B. 48 (1993) 10052
[24] K. Matsuzaki, H. Hidenori et al., Thin Solid Films 496 (2006) 37
[25] M. Orita, H. Hiramatsu, H. Ohta, M. Hirano, H. Hosono, Thin Solid Films 411(2002) 134
[26] Z. Hajnal, J. Miro et al., J. Appl. Phys. 86 (1999) 3792
[27] T. Minami, Shirai, T. Nakatani, Jpn. J. Appl. Phys. 39 (2000) L524
[28] M. Fleischer, H. Meixner, J. Appl. Phys. 74 (1993) 300
[29] T. Miyata, T. Nakatani, T. Minami, J. Lumin. 87-89 (2000) 1183
[30] L. Binet, D. Gourier, J. Phys. Chem. Solids 59 (1998) 1241
[31] G Gundiah, A. Govindaraj, C.N.R. Rao, Chem. Phys. Lett. 351 (2002) 189
[32] J. Zhang, F.H. Jiang, Chem. Phys. 289 (2003) 243
[33] M. Fleischer, H. Meixner, Sensor Actuat. B. 4 (1991) 437
[34] C. Baban, Y. Toyoda, M. Ogita, Thin Solid Films, 484 (2005) 369
[35] Y. X. Li, A. Trinchi et al., Sensor Actuat. B. 93 (2003) 431
[36] P. Sandvik, K. Mi, F. Shahedipour et al., J. Cryst. Growth 231 (2001) 366
[37] C. Sungryong, L. Jongwon et al., Mater. Lett. 57 (2002) 1004
[38] D. Stodilka, A.H. Kitai, Z. Huang et al., SID 00 DIGEST (2000) 11
[39] T. Minami, Y. Kubota, T. Miyata, H. Yamada, SID 98 DIGEST (1998) 953
[40] E. Savarimuthua, K.C. Lalithambikad et al., J. Phys. Chem. Solids 68 (2007) 1380
[41] W.S. Seo, H.H. Jo, K. Lee, J.T. Park, Adv. Mater. 15 (2003) 795
[42] E. Burstein, Phys. Rev. 93 (1954) 632
[43] J.C. Fan and J.B. Goodenough, J. Appl. Phys. 48 (1977) 3524
[44] 李家亮,姜洪义,牛金叶等,现代技术陶瓷107(2006)19
[45] J. Strumpfel* and C. May, Vacuum 59 (2000) 500
[46] J. George and C.S. Menon, Surf. Coat. Tech. 132 (2000) 45
[47] M.J. Alam and D.C. Cameron, Thin Solid Films 377 (2000) 455
[48] C.G. Granqvist and A. Hultaker, Thin Solid Films 411 (2002) 1
[49] A. Rogozin, N. Shevchenko, M. Vinnichenko et al., Appl. Phys. Lett. 85(1) (2004) 212
[50] W.F. Wu and B.S. Chiou, Appl. Surf. Sci. 68(4) (1993) 497
[51] I. Baia, M. Quintela, L. Mendes et al., Thin Solid Films 337(1-2) (1999) 171
[52] H. Ohta, M. Hirano et al., Appl. Phys. Lett. 76 (2000) 2740
[53] H. Kim, J.S. Horwitz, G.P. Kushto et al., Appl. Phys. Lett. 78 (2001) 1050
[54] M. F. A. M. van Hest, M.S. Dabney, J.D. Perkins et al., Appl. Phys. Lett. 87 (2005)032111
[55] R.K. Grupta, K. Ghosh, R. Patel, P.K. Kahol, J. Cryst. Growth 310 (2001) 4336
[56] J. Tamaki, C. Naruo, Y. Yamamoto, M. Matsuoka, Sensor Actuat. B:Chem. 83 (2002) 190
[57] P. Bogdanov, M. Lvanovskaya et al., Sensor Actuat. B:Chem. 57 (1999) 153
[58] V. Romanovskaya, M. Lvanovskaya, P. Bogdanov, Sensor Actuat. B:Chem. 56 (1999)31
[59] Akiyoshi Hattori, Hirokazu Tachibana et al., Sensor Actuat. A:Phys. 77 (1999) 120
[60] Hiroyuki Yamaura, Koji Moriya et al., Sensor Actuat. B:Chem. 65 (2000) 39
[61] Y.F. Zhang, J.Y. Li et al., Scripta Mater. 56 (2007) 409
[62] C.H. Liang, GW. Meng, Y. Lei et al., Adv. Mater. 13 (2001) 1330
[63] G. A. Rozgonyi, and W. J. Polito, Appl. Phys. Lett. 8 (1966) 220
[64] G L. Dybwad, J. Appl. Phys. 42 (1971) 5192
[65] T. Mitsuyu, S. Ono, and K. Wasa, J. Appl. Phys. 51 (1980) 2464
[66] C. Baban, Y. Toyoda, M. Ogita, Thin Solid Films, 484 (2005) 369
[67] Naoki Ohashi, Tsuyoshi Oginoa et al., J. Cryst. Growth 206 (2005) 99
[68] S. Kaleemulla, A. Sivasankar Reddy, S. Uthanna, Mater. Lett. 61 (2007)4309
[69] P. Nath and R. F. Bunshah, Thin Solid Films 69 (1980) 63
[70] K. F. Huang, T. M. Uen, Y.S. Gou et al., Thin Solid Films 148 (1987) 7
[71] H. U. Habermeier, Thin Solid Films 80 (1981) 157
[72] H. Ohta, M. Orita, M. Hirano et al., Appl. Phys. Lett. 76 (2000) 2740
[73] F. O. Adurodija, H. Izumi, T. Ishihara et al., J. Appl. Phys. 88 (2000) 4175
[74] H. Izumi, F.O. Adurodija, T. Kaneyoshi et al., J. Appl. Phys. 91 (2002) 1213
[75] K. Matsuzaki, H. Hiramatsu, K. Nomura et al., Thin Solid Films 496 (2006) 37
[76] J. R. Arthur and J. J. LePore, J. Vac. Sci. & Tecnnol. 6 (1969) 545
[77] M. A. L. Johnson, J. D. Brown, N. A. EI-Masry, J. W. Cook Jr., J. F. Schetzina, H. S. Kong, J. A. Edmond, J. Vac. Sci. Technol. B 16 (1998) 1282
[78] T. Oshima, N. Arai, N. Suzuki, Thin Solid Films 516 (2008) 5768
[79] Y. Sawada,C. Kobayashi, S. Seki, Thin Solid Films 409 (2002) 46
[80] Y. Zhang, H. Ago et al., J. Cryst. Growth 264 (2004) 363
[81] H.W. Kim, N.H. Kim, Mater. Sci. Eng. B 110 (2004) 34
[82] Ch.Y. Wang, M. Ali, Th. Kups et al., Sensor Actuat. B. 130 (2008) 589
[83] J. S. Kim, Phys.Stat.Sol. 187, No.2, 569-573 (2001)
[84] D.P. Yu, J.-L. Bubendorff, Solid State Commun. 124 (2002) 417-421
[85]Nam Ho Kim, Appl. Surf. Sci. 242 (2005) 29-34
[86] C.H. Liang, GW. Meng et al., Adv. Mater. 13 (2001) 1330
[87] H. Ohta, K. Nomura, H. Hiramatsu, Solid State Electron. 47 (2003) 2261
[88] D.D. Edwards, P.E. Folkins, T.O. Mason, J. Am. Ceram. Soc. 80 (1997) 253
[89] L. Binet, G Gauthier, C. Vigreux, D. Gourier, J. Phys. Chem. Solids 60 (1999) 1755
[90] R.J. Cava, J.M. Phillips et al., Appl. Phys. Lett. 64 (1994) 2071
[91] J.M. Phillips, J. Kwo et al., Appl. Phys. Lett. 65 (1994) 115
[92] T. Minami, Y. Takeda et al., J. Vac. Sci. Technol. A 15(3) (1997) 958
[93] J. Jeong et al., Solid State Commu. 127 (2003) 595
[94] A. Bourlange, D.J. Payne et al., Appl. Phys. Lett. 92 (2008) 092117
[95] S.Choopun, R.D.Vispute, et al., Appl. Phys. Lett. 80 (2002) 1529
[96] T.Minemoto, T.Negami, et al., Thin Solid Films 372 (2000) 173
[97] D.D. Edwards, T.O. Mason et al., J. Solid State Chem. 150 (2000) 294
[98] R. Hill, J. Phys. C: Solid State Phys. 7 (1974) 521
[1]H.M. Manasevit, Appl. Phys. Lett. 12 (1968) 156
[2]杨树人,丁墨元,《外延生长技术》,国防工业出版社,1992
[3]杨邦朝,王文生,《薄膜物理与技术》,电子科技大学出版社,1994
[4]H.M. Manasevit, W.I. Simpson, J. Electronchem. Soc. 12 (1968) 156
[5]H.M. Manasevit, J. Cryst. Growth 13 (1972) 306
[6]J. S. Roberts et al., J. Cryst. Growth, 68 (1984) 42
[7]杨于兴,漆璿,《X射线衍射分析》,上海交通大学出版社,1994
[8]左演声,陈文哲,梁伟,《材料现代分析方法》,北京工业大学出版社,2000
[9]C. G. Fonstad, R. H. Rediker, J. Appl. Phys. 42 (1971) 2911
[10]王建祺,《电子能谱学(XPS/XAES/UPS)引论》,国防工业出版社,1992
[1] D. Briggs, M.P. Seah, Practical Surface Analysis, vol. 1, Wiley, New York, 1990, p.609
[2] J.F. Moulder, W.F. Stickle, P.E. Sobol et al., Handbook of X-ray Photoelectron Spectroscopy [M], Minnesota: Physical Electronics, Inc, 1995
[3] V.K. Josepovits, O. Krafcsik, G Kiss, I.V. Perczel, Sensor Actuat. B. 48 (1998)373
[4] F. M. Amanullah, K. J. Pratap, V.H. Babu, Mater. Sci. Eng. B 52 (1998) 93
[5] A. Srinivasan, K. Jagannathan et al., Indian J. Chem. Soc. A18 (1979) 463
[6] X.J. Zhang, H.L. Ma, Q.P. Wang et al., Chinese Phys. Lett. 22 (2005) 995
[1] H. Haitjema, J.J. Ph. Elich, Thin Solid Films, 205 (1991) 93
[2] T. Koida, M. Kondo, Appl. Phys. Lett. 89 (2006) 082104
[3] J.J. Prince, S. Ramamurthy et al, J. Cryst. Growth 240 (2002) 142
[4] J. Striimpfel, C. May, Vacuum 59 (2000) 500
[5] S. Kaleemulla, A.S. Reddy et al., Mater. Lett. 61 (2009) 4309
[6] Ch.Y. Wang, V. Cimalla et al., Thin Solid Films, 130 (2008) 589
[1] Minami T, Takeda Y 1996 J . Vac . Sci. Technol. A . 15 958
[2] J.F. Moulder et al., Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer Corporation, 1979.
[3] W.K. Chu, J.W. Mayer, M.A. Nicolet, Backscattering Spectrometry, Academic,1978, pp. 150
[4] M. Orita, H. Ohta, M. Hirano, and H. Hosono, Appl. Phys. Lett. 77 (2000) 4166
[5] H.D. Xiao, H.L. Ma, C.S. Xue, H. Z. Zhuang, Mater. Chem. Phys. 101 (2007) 99
[6] X.C. Wu, J.M. Hong, Z.J. Han, Y.R. Tao, Chem. Phys. Lett. 373 (2003) 28
[7] J. Zhang, F.H. Jiang, Chem. Phys. 289 (2003) 243
[8] G. Gundiah, A. Govindaraj, C.N.R. Rao, Chem. Phys. Lett. 351 (2002) 189
[9] L. Binet, D. Gourier, J. Phys. Chem. Solids 59 (1998) 1241
[10] V.I. Vasil' tsiv, Ya.M. Zakharko, Ya.I. Prim, Ukr. Fiz. Zh. 33 (1988) 1320
[1] T. Minami, H. Nanto, S. Shooji, S. Takata, Thin Solid Films 111 (1984) 167
[2] E. Burstein, Phys. Rev. 93 (1954) 632
[1] I.Hamberg, C.G. Granqvist, J. Appl. Phys. 60 (1986) R123.
[2] M.Mizuhashi, Thin Solid Films 70 (1980) 91.
[3] B.G Lewis, D.C. Paine, MRS Bull. 25 (2000) 22.
[4] Y. Zhang, H. Ago, J. Liu, M. Yumura, K. Uchida, S. Ohshima, S. Iijima, J. Zhu, X. Zhang, J. Cryst. Growth 264 (2004) 363.
[5] C. Kuo, S. Lu, T. Wei, J. Cryst. Growth 285 (2005) 400.
[6] C. Falcony, J.R. Kirtley, D.J. Dimaria, T.P. Ma, T.C. Chen, J. Appl. Phys. 58 (1985) 3556.
[7] C.G. Granqvist, Appl. Phys., A Mater. Sci. Process. 57 (1993) 19.
[8] J. Lao, J. Huang, D. Wang, Zhifeng Ren, Adv. Mater. 16 (2004) 65.
[9] J. Joseph Prince, S. Ramamurthy, B. Subramanian, C. Sanjeeviraja, M. Jayachandran, J. Cryst. Growth 240 (2002) 142.
[10] J.Q. Hu, F.R. Zhu, J. Zhang, H. Gong, Sens. Actuators B 93 (2003) 175.
[11] T. Koida, M. Kondo, Appl. Phys. Lett. 89 (2006) 082104.
[12] T. Maruyama, K. Fukui, J. Appl. Phys. 70 (1991) 3848.
[13] A. Gurlo, M. Ivanovskaya, A. Pfau, U. Weimar, W. Gopel, Thin Solid Films 307 (1997) 288.
[14] Ch.Y. Wang, V. Cimalla, H. Romanus, Th. Kups, M. Niebelschutz, O. Ambacher, Thin Solid Films 515 (2007) 6611.
[15] W.S. Seo, H.H. Jo, K. Lee, J.T. Park, Adv. Mater. 15 (2003) 795.
[16] L.C. Chen, W.H. Lan, R.M. Lin, H.T. Shen, H.C. Chen, Appl. Surf. Sci. 252 (2006) 8438.
[17] P. Thilakan, J. Kumar, Vacuum 48 (1997) 463.
[1] K. Yanagawa, Y. Ohki, T. Omata, H. Hosono, N. Ueda, H. Kawazoe, Appl. Phys. Lett. 65 (1994) 406.
[2] D.D. Edwards, T.O. Mason, F. Goutenoire, K.R. Poeppelmeier, Appl. Phys. Lett. 70(1997)1706.
[3] A.K. Sharma, J. Narayan, J.F. Muth, C.W. Teng, C. Jin, A. Kvit, R.M. Kolbas, O.W. Holland, Appl. Phys. Lett. 75 (1999) 3327.
[4] T. Minami, Y. Takeda, T. Kakumu, S. Takata, J. Vac. Sci. Technol. A. 15 (1996 )958.
[5] G.B. Palmer, K.R. Poeppelmeier, Solid. State. Sci. 4 (2002) 317.
[6]T. Moriga, M. Mikawa, Y. Sakakibara, Thin Solid Films 4986 (2005) 53.
[7] A. Ohtomo, M. Kawasaki, T. Koida, K. Masubuchi, H. Koinuma, Y. Sakurai, Y. Yoshida, T. Yasuda, Y. Segawa, Appl. Phys. Lett. 72 (1998) 2466.
[8] H. Tanaka, S. Fujita, Appl. Phys. Lett. 86 (2005) 192911.
[9] H. Ohta, M. Orita, M. Hirano, H. Tanji, H. Kawazoe, H. Hosono, Appl. Phys. Lett. 76 (2000) 2740.
[10] J. Joseph Prince, S. Ramamurthy, B. Subramanian, C. Sanjeeviraja, M. Jayachandran, J. Cryst. Growth 240 (2002) 142.
[11] T.J. Courts, D.L. Young, X. Li, MRS Bull. 25 (2000) 58.
[12] N. Ueda, H. Hosono, R. Waseda, H. Kawazoe, Appl. Phys. Lett. 70 (1997) 3561.
[13] M. Orita, H. Ohta, M. Hirano, and H. Hosono, Appl. Phys. Lett. 77 (2000) 4166.
[14] R. Hill, J. Phys. C: Solid State Phys. 7 (1974 )521.
[15] W.K. Chu, J.W. Mayer, Backscattering Spectrometry, Academic, 1978, p. 150.