Xianjin Feng

Preparation and characterization of single crystalline anatase TiO2 films on LSAT (001) by MOCVD

TiO2 thin films with anatase structure have been prepared on [LaAlO3]0.3[SrAl0.5Ta0.5O3]0.7 (LSAT) (001) substrates by metalorganic chemical vapor deposition (MOCVD) in the substrate temperature range of 500–650 °C. Tetrakis-dimethylamino titanium (TDMAT) is used as the organometallic source and oxygen as oxidant. Structural and optical properties of the films as well as the epitaxial mechanism have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and optical transmittance spectra. The measurements and analyses show that the TiO2 film grown at 550 °C exhibits the best crystallinity with anatase structure. The obtained TiO2 film is a single-crystalline epitaxial film with no twins and very few defects. The heteroepitaxial relationship is determined as TiO2 (001) ‖ LSAT (001) with TiO2 [100] ‖ LSAT 〈100〉. The average transmittance of the film deposited at 550 °C in the visible wavelength is about 84% with an optical band gap of about 3.27 eV.

Performance enhancement of AlGaN/AlN/GaN high electron mobility transistors by thermally evaporated SiO passivation

A surface passivation technique has been developed for AlGaN/AlN/GaN high electron mobility transistors (HEMTs) by simple thermal evaporation of silicon monoxide (SiO) at room temperature. Detailed device characteristics were studied and compared with the most commonly used SiNx passivation grown by plasma enhanced chemical vapor deposition at elevated temperatures. Both passivation techniques lead to a similar enhancement in the on-state drain current and transconductance as compared with the unpassivated HEMTs. However, we discovered that the gate leakage current in the SiO passivated devices was more than two orders of magnitude lower than the devices passivated by SiNx. Furthermore, while the SiNx passivated HEMTs exhibited a two orders of magnitude increase in off-state drain current, SiO passivation substantially reduced it, resulting in an overall improvement by a factor of 1429. The extent of the device surface damage caused by passivation was also investigated by characterizing other parameters. ...

Structural and optical properties of Al2xIn2−2xO3 films prepared by metal-organic chemical vapor deposition

Tunable band gap Al2xIn2−2xO3 films with different compositions x[Al/(Al + In) atomic ratio] were grown on MgO (110) substrates by the metal organic chemical vapor deposition (MOCVD) method at a temperature of 700 °C. The effects of different Al concentrations on the structural and optical properties of the obtained films were discussed in detail. The film deposited with an Al concentration of x = 0.1 showed single crystalline bixbyite In2O3 structure with Al0.2In1.8O3 (110)‖MgO (110), while the films with x = 0.3 and 0.5 had polycrystalline structures, and the sample prepared with x = 0.9 exhibited γ-Al2O3 structure. The transmittances of all the samples exceeded 80% in the visible region. The optical absorption edges of the films shifted to short wavelength, and the bandgap of the prepared films could be monotonously modulated from 3.73 eV to 5.82 eV as the Al concentration increased from 0.1 to 0.9.

Structural, electrical and optical properties of epitaxial Ta-doped titania films by MOCVD

This work presented a detailed study on epitaxial Ta-doped titania (TiO2:Ta) films deposited via a metal organic chemical vapor deposition method. The effects of Ta dopant concentration on the film microstructure and functional characteristics including electrical and optical properties were systematically explored. The results indicated the deposited TiO2:Ta films exhibit high crystallization quality, good transparency (>92%) in the visible range, and tunable electrical properties. The maximum carrier mobility (15.4 cm2 V−1 s−1) and minimum resistivity (8.2 × 10−2 Ω cm) were achieved at Ta concentrations of 1.0% and 4.0%, respectively. The optical band gaps of the deposited films increased from 3.48 to 3.57 eV with the increase of Ta concentration from 0 to 8.0%.

Synthesis and characterization of structural and optical properties of single crystalline a-TiO2 films on MgAl2O4(111) substrate

Anatase phase TiO2 (a-TiO2) films have been deposited on MgAl2O4(111) substrates by the metal organic chemical vapor deposition (MOCVD) method at the substrate temperatures of 500-650°C. The structural analyses showed that the films were highly (004) oriented with tetragonal anatase structure and the epitaxial relationship was given as a-TiO2(004)||MgAl2O4 (111). The sample prepared at 600°C exhibited the best crystallization with a single-crystalline epitaxial film. The average transmittance of every TiO2 film in the visible range exceeded 90% excluding the influence of the substrate. The morphology and composition of the TiO2 films have also been studied in detail.

Preparation and characterization of Al{sub 2x}In{sub 2−2x}O{sub 3} films deposited on MgO (1 0 0) by MOCVD

Highlights: • Ternary Al{sub 2x}In{sub 2−2x}O{sub 3} alloy films were deposited on MgO (1 0 0) by MOCVD. • The microstructure of the Al{sub 2x}In{sub 2−2x}O{sub 3} films were studied upon HRTEM. • Al{sub 2x}In{sub 2−2x}O{sub 3} alloy films exhibited great optical transparency in the visible wavelength range. • The band gap of the Al{sub 2x}In{sub 2−2x}O{sub 3} films can be modulated by controlling the Al contents in the samples. - Abstract: The ternary Al{sub 2x}In{sub 2−2x}O{sub 3} films with different compositions x[Al/(Al + In) atomic ratio] have been fabricated on the MgO (1 0 0) substrates by the metal organic chemical vapor deposition (MOCVD) method. The influence of different Al contents on the structural, optical and electrical properties of Al{sub 2x}In{sub 2−2x}O{sub 3} films has been studied. The structural studies reveal a change from single crystalline structure of cubic In{sub 2}O{sub 3} to amorphous as the Al content increases. The average transmittances of all samples in the visible range are over 80%. The optical band gap is observed to increase monotonically from 3.67 to 5.38 eV as the Al content increases from 0.1 to 0.9.

Structure and Optical Properties of Epitaxial Indium Oxide Films Deposited on Y-Stabilized ZrO2 (111) by MOCVD

Indium oxide (In2O3) films have been deposited on Y-stabilized ZrO2 (YSZ) (111) substrates, at temperatures from 500°C to 700°C, by metal–organic chemical vapor deposition. Structural analysis indicated that all the films were cubic bixbyite In2O3 with an out-of-plane relationship of In2O3 (222)||YSZ (111). Crystal quality was best for the film prepared at 600°C. The microstructure of this film was investigated by high-resolution transmission electron microscopy. A theoretical model is proposed for the mechanism of growth, and the in-plane epitaxial relationship of the single crystalline In2O3 film on the YSZ (111) substrate was shown to be In2O3

Structural and photoluminescence properties of single-crystalline In2O3 films grown by metal organic vapor deposition

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