A study of Inx Ga1-x N growth by reflection high-energy electron diffraction

Epitaxial growth of Inx Ga1-x N alloys on GaN (0001) by plasma-assisted molecular-beam epitaxy is investigated using the in situ reflection high-energy electron-diffraction (RHEED) technique. Based on RHEED pattern changes over time, the transition of growth mode from two-dimensional (2D) nucleation to three-dimensional islanding is studied for various indium compositions. RHEED specular-beam intensity oscillations are recorded during the 2D wetting-layer growth, and the dependences of the oscillation period/frequency on the substrate temperature and source flux are established. By measuring the spacing between diffraction spots in RHEED, we also estimated indium composition, x, in alloys grown under different flux combinations. Incorporation coefficients of both gallium and indium are derived. Possible surface segregation of indium atoms is finally examined. © 2005 American Institute of Physics.published_or_final_versio

Coherent and dislocated three-dimensional islands of Inx Ga1-x N self-assembled on GaN(0001) during molecular-beam epitaxy

Molecular-beam epitaxy of Inx Ga1-x N alloy on GaN(0001) is investigated by scanning tunneling microscopy. The Stranski-Krastanov mode of growth of the alloy is followed, where the newly nucleated three-dimensional islands are initially coherent to the underlying GaN and the wetting layer, but then become dislocated when grown bigger than about 20 nm in the lateral dimension. Two types of islands show different shapes, where the coherent ones are cone shaped and the dislocated ones are pillar like, having flat-tops. Within a certain range of material coverage, the surface contains both coherent and dislocated islands, showing an overall bimodal island-size distribution. The continued deposition on such surfaces leads to the pronounced growth of dislocated islands, whereas the sizes of the coherent islands change very little. © 2005 The American Physical Society.published_or_final_versio

Growth mode and strain evolution during InN growth on GaN(0001) by molecular-beam epitaxy

The plasma-assisted molecular-beam epitaxy technique was used to study the epitaxial growth of InN on GaN. A relationship between film growth mode and the deposition condition was established by combining reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). The sustained RHEED intensity oscillations were recorded for 2D growth while 2D nucleation islands were revealed by STM. Results showed less than three oscillation periods for 3 D growth, indicating the Strnski-Krastanov (SK) growth mode of the film.published_or_final_versio

InN Island shape and its dependence on growth condition of molecular-beam epitaxy

The three-dimensional (3D) island shapes of the InN and its dependence on growth conditions of molecular-beam epitaxy (MBE) were analyzed. The islands were dislocated and the strain in an island depended on its size. The pillar-shaped islands with low aspect ratios represented the equilibrium shape, and the pyrimidal islands with higher aspect ratios were limited by kinetics during MBE growth. The decreasing trend of island aspect ratio with respect to island size was attributed to gradual relaxation of residual strain in dislocated islands.published_or_final_versio

Geochemical Constrains on Nature of Source Region of The Late Permian Emeishan Continental Flood Basalts, SW China

Abstract in http://www.lpi.usra.edu/meetings/gold2001/pdf/3488.pd

Comparison of legal system of occupational safety and health between Hong Kong and Mainland China

2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Scaling of three-dimensional InN islands grown on GaN(0001) by molecular-beam epitaxy

The scaling property of three-dimensional InN islands nucleated on GaN(0001) surface during molecular-beam epitaxy (MBE) is investigated. Due to the large lattice mismatch between InN and GaN (∼10%), the islands formed from the Stranski-Krastanow growth mode are dislocated. Despite the variations in (residual) strain and the shape, both the island size and pair separation distributions show the scaling behavior. Further, the size distribution resembles that for submonolayer homoepitaxy with the critical island size i = 1, suggesting that detachment of atoms is not significant. The above results also indicate strain is insignificant in determining the nucleation and growth of dislocated islands during heteroepitaxy by MBE.published_or_final_versio

In situ revelation of a zinc-blende InN wetting layer during Stranski-Krastanov growth on GaN(0001) by molecular-beam epitaxy

Indium nitride (InN) exists in two different structural phases, the equilibrium wurtzite (w) and the metastable zinc-blende (zb) phases. It is of scientific interest and practical relevance to examine the crystal structure of the epifilms during growth. In this paper, we use Patterson function inversion of low-energy electron diffraction I-V curves to reveal the preferential formation of zinc-blende InN wetting layer during the Stranski-Krastanov growth on GaN(0001). For three-dimensional islands nucleated afterwards on top of the wetting layer and for thick InN films, the equilibrium wurtzite structure is observed instead. This in situ revelation of the InN lattice structure is confirmed by ex situ transmission electron microscopy studies. Finally, the formation of zb-InN layer on w-GaN is explained in terms of the strain in the system. © 2005 The American Physical Society.published_or_final_versio

Arc Discharge Synthesis and Photoluminescence of 3D Feather-like AlN Nanostructures

A complex three-dimensional (3D) feather-like AlN nanostructure was synthesized by a direct reaction of high-purity Al granules with nitrogen using an arc discharge method. By adjusting the discharge time, a coral-like nanostructure, which evolved from the feather-like nanostructure, has also been observed. The novel 3D feather-like AlN nanostructure has a hierarchical dendritic structure, which means that the angle between the trunk stem and its branch is always about 30° in any part of the structure. The fine branches on the surface of the feather-like nanostructure have shown a uniform fish scale shape, which are about 100 nm long, 10 nm thick and several tens of nanometers in width. An alternate growth model has been proposed to explain the novel nanostructure. The spectrum of the feather-like products shows a strong blue emission band centered at 438 nm (2.84 eV), which indicates their potential application as blue light-emitting diodes