Jr-Sheng Tian

Growth of nonpolar (112¯0) ZnO films on LaAlO3 (001) substrates

Nonpolar (112¯0) ZnO films were grown on LaAlO3 (001) single crystal substrates at temperature from 300 to 750 °C by pulsed laser deposition method. The films were examined using x-ray diffraction, reflection high energy electron diffraction, and photoluminescence measurements for the crystallinity. The surface morphology of ZnO films from atomic force microscopy exhibits L-shaped domains. Cross-sectional transmission electron microscopy with selected area diffraction reveals two types of a-plane ZnO domains perpendicular to each other with in-plane orientation relationships of [0001]ZnO∥[11¯0]LAO and [11¯00]ZnO∥[11¯0]LAO.

Indium-rich InAlN films on GaN/sapphire by molecular beam epitaxy

Here, we report the results of characterization of indium (In)-rich InAlN films on GaN/Sapphire (0001) substrates grown by molecular beam epitaxy. The high-quality ~123 nm thick InAlN films with 85% In content without phase separation were assessed with x-ray diffraction and transmission electron microscopy (TEM) with x-ray energy dispersive spectroscopy. High-resolution TEM analysis reveals the relaxation at InAlN/GaN interface with misfit dislocations of 1.59 nm spacing. Finally, optical and electrical properties of the InAlN films are presented from absorption spectroscopy and Hall measurements.

The cooling effect on structural, electrical, and optical properties of epitaxial a-plane ZnO:Al on r-plane sapphire grown by pulsed laser deposition

Here, the unambiguous effect of cooling rate on structural, electrical, and optical properties of a-plane ZnO:Al on r-plane sapphire grown by pulsed laser deposition at 700 °C is reported. A high cooling rate (∼100 °C/min) can result in stripe morphology along m-direction and significant deformation on the epitaxial films of a-plane ZnO:Al with deteriorated crystallinity and significantly lowered resistivity. Also, photoluminescence spectra exhibit high intensities of excess violet and green emissions with low intensity of near band edge luminescence. Comparison with pure a-plane ZnO films is also presented.

The Effect of Tensile Strain on Optical Anisotropy and Exciton of

The near band edge emission of the tensile-strained m-plane ZnO film grown on (112)LaAlO3 substrates shows abnormal low polarization degree (ρ = 0.1). The temperature dependency of polarization degree clarifies the origins of different emission peaks. In tensile-strained m-plane ZnO, the [0001] polarized state is upper shifted and is overlapping with the [112̅0] polarized state. This phenomenon causes the abnormal low polarization degree and reveals the effect of strain on the emission anisotropy of m-plane ZnO.

m

The microstructure of semipolar [Formula: see text] ZnO deposited on (112) LaAlO3/(La,Sr)(Al,Ta)O3 was investigated by transmission electron microscopy. The ZnO shows an in-plane epitaxial relationship of [Formula: see text] with oxygen-face sense polarity. The misfit strain along [Formula: see text] and [Formula: see text] is relieved through the formation of misfit dislocations with the Burgers vectors [Formula: see text] and [Formula: see text], respectively. The line defects in the semipolar ZnO are predominantly perfect dislocations, and the dislocation density decreases with increasing ZnO thickness as a result of dislocation reactions. Planar defects were observed to lie in the M-plane and extend along 〈0001〉, whereas basal stacking faults were rarely found.

-Plane ZnO

The microstructure of semipolar [Formula: see text] ZnO deposited on (112) LaAlO3/(La,Sr)(Al,Ta)O3 was investigated by transmission electron microscopy. The ZnO shows an in-plane epitaxial relationship of [Formula: see text] with oxygen-face sense polarity. The misfit strain along [Formula: see text] and [Formula: see text] is relieved through the formation of misfit dislocations with the Burgers vectors [Formula: see text] and [Formula: see text], respectively. The line defects in the semipolar ZnO are predominantly perfect dislocations, and the dislocation density decreases with increasing ZnO thickness as a result of dislocation reactions. Planar defects were observed to lie in the M-plane and extend along 〈0001〉, whereas basal stacking faults were rarely found.

Defects in semipolar

This paper reports on high-quality InN materials prepared on a GaN template using radio-frequency metalorganic molecular beam epitaxy. We also discuss the structural and electro-optical properties of InN nanorods/films. The X-ray diffraction peaks of InN(0002) and InN(0004) were identified from their spectra, indicating that the (0001)-oriented hexagonal InN was epitaxially grown on the GaN template. Scanning electron microscopic images of the surface morphology revealed a two-dimensional growth at a rate of approximately 0.85 μm/h. Cross-sectional transmission electron microscopy images identified a sharp InN/GaN interface and a clear epitaxial orientation relationship of [0001]InN // [0001]GaN and (2¯110)InN // (2¯110)GaN. The optical properties of wurtzite InN nanorods were determined according to the photoluminescence, revealing a band gap of 0.77 eV.

(1 1\bar {2}\bar {2})

The effect of growth temperature on a-plane ZnO formation on r-plane sapphire has been systematically investigated by employing in situ high pressure reflection high-energy electron diffraction, atomic force microscopy, and high-resolution x-ray diffraction. For film growth above and below 600 °C, it is shown that there is a significant difference in growth rate and surface morphology due to the differences in the growth mode. Stripelike morphologies were observed on the surface of a-plane ZnO grown at low temperature (LT) because of differences in the growth rate along the c-axis and the growth rate normal to the c-axis. Furthermore, annealing of films grown at low temperature results in more pronounced stripe morphology and in improvement of crystallinity.

ZnO grown on (112) LaAlO3/(La,Sr)(Al,Ta)O3 substrate by pulsed laser deposition

The defects in (134¯0)ZnO epitaxial film grown on (114)LaAlO3 (LAO) have been systematically investigated by using transmission electron microscopy. At the ZnO/LAO interface, the Burgers vectors of misfit dislocations are identified to be 1/3[1¯21¯0] and 1/2[0001]. Threading dislocations with the Burgers vectors of 1/3⟨112¯0⟩ and ⟨0001⟩ are distributed on the basal plane. In (134¯0)ZnO film, the predominant planar defects are basal stacking faults (BSFs) with 1/6⟨202¯3⟩ displacement vectors. The densities of dislocations and BSFs are about 3.8 × 1010 cm−2 and 3.1 × 105 cm−1, respectively.

Defects in semipolar (11(2)over-bar(2)over-bar) ZnO grown on (112) LaAlO3/(La, Sr) (Al, Ta)O-3 substrate by pulsed laser deposition

The defects in (134¯0)ZnO epitaxial film grown on (114)LaAlO3 (LAO) have been systematically investigated by using transmission electron microscopy. At the ZnO/LAO interface, the Burgers vectors of misfit dislocations are identified to be 1/3[1¯21¯0] and 1/2[0001]. Threading dislocations with the Burgers vectors of 1/3⟨112¯0⟩ and ⟨0001⟩ are distributed on the basal plane. In (134¯0)ZnO film, the predominant planar defects are basal stacking faults (BSFs) with 1/6⟨202¯3⟩ displacement vectors. The densities of dislocations and BSFs are about 3.8 × 1010 cm−2 and 3.1 × 105 cm−1, respectively.