Reactive Gas-timing RF Magnetron Sputtering Research Articles

Spectroscopic study on amorphous tantalum oxynitride thin films prepared by reactive gas-timing RF magnetron sputtering

The amorphous tantalum oxynitride (TaOxNy) thin films were prepared on silicon (100) substrates by magnetron sputtering system with different techniques of conventional reactive sputtering and reactive gas-timing (RGT). The films were studied via spectroscopic ellipsometry (SE) measured in the range of 0.75–5.0 eV with 0.025 eV interval at 70° incident angle, and the optical model based on Tauc-Lorentz function was constructed to extract the properties of the films. The SE results indicated that all prepared films were grown homogeneously and show different optical properties upon their deposition conditions and techniques. The optical properties of film prepared by conventional reactive sputtering were close to the tantalum oxide film (TaO). The refractive index and optical band gap (Eg) of RGT samples changed with the oxygen timing and correlated with the change of oxygen and nitrogen concentration of the films. In addition, the morphologies, crystallinities, atomic concentrations and distributions of nitrogen atoms in the films analyzed by field-emission scanning electron microscopy, glazing-incident X-ray diffraction, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy are also discussed.

Observations of the initial stages on reactive gas-timing sputtered TaO thin films by dynamic in situ spectroscopic ellipsometery

Dynamic in-situ spectroscopic ellipsometry (iSE) was employed to investigate the growth mechanism of the tantalum oxide (TaO) film on silicon wafer substrate deposited by reactive gas-timing RF magnetron sputtering compared with conventional reactive sputtering. The effect of reactive gas timing parameter on physical structure and optical property were analyzed by both the continuous and island film growth model with Tauc-Lorentz optical model. The variation of refractive index, film thickness and void volume fraction were obtained from dynamic fits of iSE data indicated that the growth process of the amorphous TaO thin films was divided into two regimes: the nucleation stage and continuous-layer stage. These stages were observed during deposition although the initial film growth stage corresponds to the island film growth model. The study demonstrates that sputtered TaO by the RGT technique at the O2 on-off gas timing has played a crucial factor in improving the formation of nucleation stage and that the deposited TaO thin films were high deposition rate with high refractive index. The complementary field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) showed a good agreement with the film thickness and morphology obtained from dynamic iSE measurement. The real-time monitoring of iSE offers important evidences to understand the growth mechanism of reactive gas-timing technique.

Optical band engineering of metal-oxynitride based on tantalum oxide thin film fabricated via reactive gas-timing RF magnetron sputtering

Abstract In this paper, we demonstrate a novel technique, as called reactive gas-timing (RGT) RF magnetron sputtering, to control and design an optical band engineering of TaON thin films without an external heating substrate temperature and post annealing treatment process. The influence of the oxygen intervals ranged from 5 to 60 s on deposition rate, chemical composition and optical properties of TaON thin films were investigated. The chemical composition was characterized by auger electron spectroscopy (AES). The optical properties were determined by UV–Vis spectrophotometer and spectroscopic ellipsometry. The nitrogen atomic concentration of the TaON thin films deposited by RGT decreased when the oxygen gas-timing intervals increased. In addition, the RGT sputtered TaON films could be demonstrated band gaps engineering from 1.90 to 2.15 eV.

Study of Structural Properties of N-Doped ZnO Thin Film Prepared by Reactive Gas-Timing RF Magnetron Sputtering

We examined structural properties of nitrogen doped (ZnO:N) thin films prepared by reactive RF magnetron sputtering technique in conjunction with gas timing method. The deposited films were polycrystalline ZnO in wurtzite structure. Morphology of the ZnO:N films could be modified by adjusting gas timing conditions. The x-ray photoelectron spectroscopy (XPS) and extended x-ray absorption fine structure (EXAFS) analysis showed that incorporation of nitrogen may cause structural distortion in the ZnO:N crystal.

Chemical Characterization and Electrical Properties of Indium Oxynitride Grown by Reactive Gas-Timing RF Magnetron Sputtering

This work investigates changes in the chemical composition of InON thin films, grown by reactive gas-timing rf magnetron sputtering with different O2:N2 timing ratio characterized by Auger Electron Microscope (AES), Raman Spectroscopy which are well correlated with the electrical properties of films. The existence of nitrogen and oxygen in the deposited InON thin films was revealed by AES. Two Raman active optical phonons have been clearly observed and assigned to InN E1(TO) at ~470 cm-1 and E1(LO) at ~570 cm-1 and also shifted with different O2:N2 timing ratio. The carrier mobility of InON thin films was decreased when the ratio of O2:N2 timing is increased.

Investigation of Oxygen Contamination in Indium Nitride Thin Film by X-Ray Absorption Fine Structure

Local structures of indium oxynitride (InON) nano-crystal prepared by reactive gas-timing RF magnetron sputtering technique are under investigation. Since the optical properties of these InON thin films depend on gas-timing ratio, the local structure analysis is needed in order to determine the relation between the gas timing ratio and its optical properties. In this work, InON thinfilm with 30:0 seconds (N2:O2) gas-timings ratio was analyzed for its local structure using X-ray absorption fine structure (XAFS) technique in conjunction with first principle calculation. The results indicate that the crystal structure of the film is wurtzite structure which is a typical structure of InN. However from the results of Auger Electron Spectroscopy (AES), there are oxygen contents in the film. Since XAFS analysis confirmed the 4-fold local structure of Indium atom, these oxygen atoms must be substituted in nitrogen sites with slightly changing the local structure of Indium atom. The best fit of XAFS data indicated that there is an oxygen atom substituted in nitrogen site of the 4-fold indium.

Nanocrystal-ZnO Thin Film Deposition by a Novel Reactive Gas-Timing RF Magnetron Sputtering Provided for UV Photodetectors

The fabrication and characterizations of nanocrystal-ZnO thin film used as active layer of MSM-photodetector structure are reported. The ZnO thin film were successfully sputtered on SiO2/Si substrates without heating or annealing processes by using a novel reactive gas-timing technique. In our experiment, the ZnO thin film properties with different gas-timing ratio of Ar/O2 were investigated. For fabricating of UV detector, the Al interdigitate electrode was deposited on SiO2/Si substrate by DC sputtering process and ZnO thin film was deposited as active layer. The response wavelength peak occurs at around 380 nm corresponding to ZnO energy bandgap of 3.2 eV .The I-V measurements indicates the Schottky behavior of ZnO on Al contact.

An extreme change in structural and optical properties of indium oxynitride deposited by reactive gas-timing RF magnetron sputtering

The indium oxynitride (InON) films were achieved by reactive RF magnetron sputtering indium target which has the purity of 99.999% with a novel reactive gas-timing technique. The structural, optical and electrical properties in a series of polycrystalline InON films affected by gas-timing of reactive N 2 and O 2 gases introduced to the chamber were observed. The X-ray photoelectron spectroscopy revealed that the oxygen content in thin films that compounded to indium and nitrogen, which increased from 10% in indium nitride (InN) to 66% in indium oxide (In 2O 3) films. The X-ray diffraction peaks show that the phase of deposited films changes from InN to InON and to In 2O 3 with an increasing oxygen timing. The hexagonal structure of InN films with predominant (0 0 2) and (0 0 4) orientation was observed when pure nitrogen is only used as sputtering gas, while InON and In 2O 3 seem to demonstrate body-center cubic polycrystalline structures depending on gas-timing. The surface morphologies investigated from atomic force microscope of deposited films with varying gas-timing of O 2:N 2 show indifferent. The numerical algorithm method was used to define the optical bandgap of films from transmittance results. The increasing oxygen gas-timing affects extremely to the change of crystallinity phase from InN to InON and to In 2O 3, the increase of optical bandgap from 1.4 to 3.4 eV and the rise of sheet resistance from 15 Ω/□ to insulator.

Photomodulated reflectance study on optical property of InN thin films grown by reactive gas-timing rf magnetron sputtering

The photoreflectance (PR) spectroscopy has been applied to investigate the band-gap energy ( E g) of indium nitride (InN) thin films grown by rf magnetron sputtering. A novel reactive gas-timing technique applied for the sputtering process has been successfully employed to grow InN thin films without neither substrate heating nor post annealing. The X-ray diffraction (XRD) patterns exhibit strong peaks in the orientation along (0 0 2) and (1 0 1) planes, corresponding to the polycrystalline hexagonal-InN structure. The band-gap transition energy of InN was determined by fitting the PR spectra to a theoretical line shape. The PR results show the band-gap energy at 1.18 eV for hexagonal-InN thin films deposited at the rf powers of 100 and 200 W. The high rf sputtering powers in combination with the gas-timing technique should lead to a high concentration of highly excited nitrogen ions in the plasma, which enables the formation of InN without substrate heating. Auger electron spectroscopy (AES) measurements further reveal traces of oxygen in these InN films. This should explain the elevated band-gap energy, in reference to the band-gap value of 0.7 eV for pristine InN films.

Growth and Characterization of Zinc Oxynitride Thin Films by Reactive Gas-Timing RF Magnetron Sputtering

Nitrogen-doped zinc oxide (N:ZnO) films on glass substrates have been prepared by the reactive gas-timing rf magnetron sputtering of ZnO targets in a mixture of argon and nitrogen gases. Using this gas-timing technique, N:ZnO films were produced without any substrate heating. The nitrogen partial pressure during the sputtering process was periodically controlled by an on-off sequence. The structural and optical properties of the fabricated films were analyzed by X-ray diffraction (XRD) and optical absorption spectroscopy, respectively. The nitrogen composition of the N:ZnO films was quantified by X-ray photoelectron spectroscopy (XPS). In this study, we focused on investigating the effects of the nitrogen flow rate and the rf power on the structural properties, the nitrogen doping efficiency, and the optical band gap of N:ZnO films. A slight shift in the optical band gap to a higher energy was found when the nitrogen flow rate was increased or when the rf power was decreased. This coincides with an improvement in the crystallinity of the films. Gas-timing rf magnetron sputtering deposition is a simple method of fine-tuning material properties by slight modifications to the existing sputtering technique.