The effects of carrier gas and substrate temperature on ZnO films prepared by ultrasonic spray pyrolysis

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• 作者：Samerkhae Jongthammanurak^a ; ^{samerkhj@mtec.or.th} ; Maetapa Witana^b ; Tinnaphob Cheawkul^b ; Chanchana Thanachayanont^a
• 关键词：Oxides ; Thin films ; Coatings ; Semiconductivity
• 刊名：Materials Science in Semiconductor Processing
• 出版年：2013
• 出版时间：June, 2013
• 年：2013
• 卷：16
• 期：3
• 页码：625-632
• 全文大小：892 K

文摘

ZnO films were deposited on glass substrates in the temperature range of 350-470 ¡ãC under an atmosphere of compressed air or nitrogen (N₂) by using ultrasonic spray pyrolysis technique. Structural, electrical and optical properties of the ZnO films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical two-probe and optical transmittance measurements. The ZnO films deposited in the range of 350-430 ¡ãC were polycrystalline with the wurtzite hexagonal structure having preferred orientation depending on the substrate temperature. The ZnO films deposited below 400 ¡ãC had a preferred (100) orientation while those deposited above 400 ¡ãC mostly had a preferred (002) orientation. The resistivity values of ZnO films depended on the types of carrier gas. The ZnO thin films deposited under N₂ atmosphere in the range of 370-410 ¡ãC showed dense surface morphologies and resistivity values of 0.6-1.1 ¦¸-cm, a few orders of magnitude lower than those deposited under compressed air. Hydrogen substition in ZnO possibly contributed to decreasing resistivity in ZnO thin films deposited under N₂ gas. The Hall measurements showed that the behavior of ZnO films deposited at 410 ¡ãC under the N₂ atmosphere was n-type with a carrier density of 8.9-9.2¡Á10¹⁶ cm^-3 and mobility of ¡«70 cm²/Vs. ZnO thin films showed transmission values at 550 nm wavelength in a range of 70-80 % . The values of band gaps extrapolated from the transmission results showed bandgap shrinkage in an order of milli electron volts in ZnO films deposited under N₂ compared to those deposited under compressed air. The calculation showed that the bandgap reduction was possibly a result of carrier-carrier interactions.