G. X. Liu

Ga2O3 THIN FILM DEPOSITED BY ATOMIC LAYER DEPOSITION WITH HIGH PLASMA POWER

Abstract Ga2O3 thin films were deposited at 200°C on p-type Si (100) by plasma-enhanced atomic layer deposition technique with an alternating supply of reactant source, [(CH3)2GaNH2]3, and high-power oxygen plasma of 180 W. The as-deposited thin films were annealed at 500, 700, 900°C in oxygen ambient for 10 min in a rapid thermal annealing system, respectively. X-ray diffractometer and atomic force microscope were used to investigate the structural properties and the surface morphologies of the thin films. The as-deposited thin film was amorphous and the thin films annealed at high temperatures were monoclinic β -phase Ga2O3. The electrical properties of Pt/Ga2O3/Si structured thin film were investigated using a semiconductor parameter analyzer. It was found that the as-deposited thin film and the thin film annealed at 500°C were leaky, however, the insulating properties of the thin films annealed at high temperatures were greatly improved. Spectroscopic ellipsometry was also used to derive the refractive indices and the thicknesses of the thin films.

TRANSPARENT TITANIUM DIOXIDE THIN FILM DEPOSITED BY PLASMA-ENHANCED ATOMIC LAYER DEPOSITION

ABSTRACT TiO2 thin films were deposited at 200°C on Si (100) and quartz substrates using plasma enhanced atomic layer deposition (PEALD) with alternating supply of reactant source, Ti[N(CH3)2]4, and oxygen plasma, and then were annealed at various temperatures in oxygen ambient using a rapid thermal annealing (RTA) system. While dielectric constant of TiO2 films slightly decreased with increasing annealing temperature, the leakage current characteristics of TiO2 films were significantly improved with increasing annealing temperature. The leakage current density of a 40 nm-TiO2 film on Si substrate annealed at 900°C was approximately 8× 10−8 A/cm2 at 150 kV/cm. All of the TiO2 thin films showed high transmittances as high as 70∼ 97% in the pertinent wavelength range and annealed TiO2 films exhibited a bandgap energy of about 3.30 eV. Raman spectra also confirmed the formation of anatase phase in TiO2 films annealed by RTA process.

HEXAGONAL ZINC OXIDE THIN FILMS ON CUBIC MGO (100) SUBSTRATES DEPOSITED BY PULSED LASER DEPOSITION

ABSTRACT Zinc oxide (ZnO) thin films were deposited on cubic MgO (100) substrates at different temperatures (100–500°C) using pulsed laser deposition. For comparison, ZnO thin films were also deposited on glass substrates. An x-ray diffractometer was used to investigate the structural properties of the thin films. It was found that the thin films on MgO substrates showed hexagonal structure with (100), (002), and (101) orientations. However, the thin films on amorphous glass substrates show c-axis oriented ZnO only. Spectrometer was used to measure the luminescent properties of the thin films. All of the thin films showed two emission peaks. One was the near band edge (NBE) emission; and the other was the visible deep-level (DL) emission. The thin film on MgO substrate grown at 300°C showed the highest luminescent peak. However, 500°C was found to be the best condition for the thin film grown on glass substrate. The DL emission decreased with time. The thin films were annealed in N2 and O2 ambient in a rapid thermal annealing system for 3 min to find the origin of the DL emission. It was found that the oxygen vacancies instead of the zinc interstitials were responsible for the DL emission.

Gallium and Nitrogen Co-Doped ZnO Thin Films by Pulsed Laser Deposition

Pulsed laser deposition (PLD) technique is a very powerful method for fabricating various oxide thin films due to its native merits. In this study, gallium and nitrogen co-doped ZnO thin films (0.1 at.%) were deposited at different temperatures (100-600°C) on sapphire (001) substrates by using PLD. X-ray diffractometer, atomic force microscope, spectrophotometer, and spectrometer were used to characterize the structural, the morphological and the optical properties of the thin films. Hall measurements were also carried out to identify the electrical properties of the thin films.

Pulsed Laser Deposition and Characterization of InZnO Alloyed Thin Film

High-quality In2O3 powder and ZnO powder had been used to make the ceramic target and the atomic ratio of 1 to 1 of indium and zinc had been prepared in this study. The alloyed thin films had been deposited on sapphire (001) substrates at different temperatures (100–600°C) by using pulsed laser deposition (PLD) technique. An x-ray diffractometer and an atomic force microscope were used to investigate the structural and morphological properties of the alloyed thin films. It was observed that the alloyed thin films deposited at the temperatures lower than 300°C were amorphous, and the alloyed thin films deposited at high temperatures were crystallized. A spectrophotometer was used to investigate the transmittances of the alloyed thin films. It was found that the alloyed thin films were of high quality. The band gap energies of the alloys were calculated by linear fitting the sharp absorption edges of the transmittance spectra. The Hall measurements were also carried out to identify the electrical properties of the thin films.

CHARACTERIZATIONS OF GALLIUM AND ARSENIC CO-DOPED ZnO THIN FILMS DEPOSITED BY PULSED LASER DEPOSITION TECHNIQUE

ABSTRACT Gallium and arsenic doped ZnO thin films (0.1 at.%) were deposited at different temperatures by using pulsed laser deposition technique. An x-ray diffractometer was used to investigate the structural properties of the thin films. It is found that the thin films have a preferred (002) orientation, and the peak intensity of the (002) orientation increases with increasing growth temperature. Atomic force microscope was used to investigate the surface morphologies of the thin films. The grain size and roughness of the thin films depend on the growth temperature. A spectrophotometer was used to measure the transmittances of the thin films. The band gap energies of the thin films were calculated by linear fitting the sharp absorption edge of high-quality thin films. It is found that, the band gap energies of gallium and arsenic co-doped ZnO thin films are larger than the pure ZnO due to Burstein-Moss effect, and the band gap energy decreases with increasing growth temperature. A spectrometer was used to investigate the luminescent properties of the thin films. All of the thin films show near band edge emission and no deep-level emissions are observed. This is believed to be the compensation of the oxygen vacancies. Hall measurements indicate that all the thin films are n-type semiconductor and the doped thin film grown at 400°C is the most conductive and has the highest mobility.

Microstructure and Electrical Properties of BLT Films by Chemical Solution Deposition

ABSTRACT The phase formation and electrical properties of (Bi,La)4Ti3O12 (BLT) thin film prepared by the chemical solution deposition method on Pt/TiO2/SiO2/Si substrates have been investigated. It was observed that the microstructure and electrical properties of BLT thin films dramatically varied with rapid thermal annealing (RTA) temperature. The crystallinity and grain size of BLT thin films were definitely increased with increasing RTA temperature of BLT films, which resulted in the enhancement of remanent polarization in BLT films. The remanent polarization (Pr) of BLT films annealed at 800°C by an RTA system was about 10 μ C/cm2. The leakage current densities of BLT films annealed above 750°C are 1∼ 3 × 10− 7A/cm2 at the applied field of 100 kV/cm. The polarization loss of BLT thin films after 1010 switch cycles is observed to slightly increase with increasing RTA temperature.