Polarity control of intrinsic ZnO films using substrate bias

Abstract

The structures and properties of zinc oxide thin films deposited by radio-frequency magnetron sputtering were investigated for different substrate biases applied during deposition. The electrical bias determined the crystalline polarity of a nominally undoped film on an amorphous substrate: films with a (0001) surface and a (0001¯) surface were produced under positive and negative biases, respectively. Moreover, the polarity of the films was determined at an early stage of the deposition and could not be reversed by switching the substrate bias.

Growth‐Parameter Dependence of Polarity and Electronic Transports in ZnO Thin Films Deposited by Magnetron Sputtering

“…Therefore, we can conclude that the VB‐XPS is an appropriate method to determine the polarity. Here, we denote two peaks (P 1 and P 2 ), and the intensity ratio between these peaks is regarded as the fingerprint of crystalline polarity . It should be noted that the polarity dependence of the VB‐XPS profile is significant when the VB‐XPS is measured for the (000 l ) surface with normal emission geometry.…”

“…All ZnO thin films were deposited on silica glass substrates using an RF magnetron sputtering method. Details of the process and instrumentation have been reported in detail elsewhere . Briefly, substrate temperature was set to 500 °C for all depositions, and P RF (30–50 W) and d s−t (50–150 mm) were independently varied.…”

“…After deposition, the electronic structures were characterized using X‐ray photoelectron spectroscopy (XPS) without an exposure to air, using a monochromated Al K α X‐ray source (1486.6 eV) for excitation. All of the XPS measurements were performed with normal emission geometry at room temperature to determine crystalline polarity of the ZnO films through characterizations of spectral features in valence band XPS (VB‐XPS) spectra . Then, the film thickness was determined by a surface profiler and the averaged deposition rate was calculated from the film thickness and deposition time.…”

“…In this sense, it is necessary to establish how to control the polarity of ZnO films on glass substrates, which can give more insight into the control of their physical properties. We have reported that an external dc bias applied to the substrates ( V sub ) during radio‐frequency (RF) magnetron sputtering enables the control of the polar structures of ZnO thin films . For instance, the sign of V sub , positive or negative, was effective in the selective fabrication of Zn‐polar (Zn‐face) and O‐polar (O‐face) ZnO thin films, respectively.…”

Conductive ZnO:Zn Composites for High-Rate Sputtering Deposition of ZnO Thin Films

“…These characteristics combined with other interesting properties, for example strong blue luminescence and a large acoustic velocity (6336 m/s), make ZnO attractive for use in many applications, including optoelectronic devices and sensors. [1][2][3][4][5][6] ZnO has been extensively studied in recent years as a potential replacement for hydrogenated amorphous or polycrystalline silicon thin film transistors (TFT) that serve as the backplane for active matrix displays, for example liquid crystal displays and organic light-emitting diodes. [7][8][9] Nanostructured ZnO (e.g.…”