Zhe Feng - Academia.edu (original) (raw)

Papers by Zhe Feng

Research paper thumbnail of Comparative investigation of high-resolution transmission electron microscopy and Fourier transform infrared spectroscopy for GaN films on sapphire substrate

Proceedings of SPIE, Nov 9, 1999

A comparative study on GaN/sapphire has been performed by transmission electron microscopy (TEM) ... more A comparative study on GaN/sapphire has been performed by transmission electron microscopy (TEM) and IR reflectance (IR). TEM observations reveal that both the undoped and Si doped GaN epilayers have large density of threading dislocations. Dislocations in ...

Research paper thumbnail of A comparative investigation of the optical properties of polar and semipolar GaN epi-films grown by metalorganic chemical vapor deposition

Semiconductor Science and Technology, Apr 22, 2022

We report on the structural and optical properties of polar gallium nitride on c-plane sapphire s... more We report on the structural and optical properties of polar gallium nitride on c-plane sapphire substrates and semi-polar (11-22) GaN films on m-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD). Polar GaN on c-plane sapphire and semi-polar GaN on m-place sapphire both show good crystal quality, luminescence, absorption, and Raman characteristics. GaN on c-place sapphire shows a high crystal quality as compared to GaN on m-plane sapphire. Surface roughness of polar GaN is lesser than semi-polar GaN. The biaxial structural stress in GaN switches from compressive to tensile as the temperature is increased. This stress-switch temperature is higher in GaN/c-plane than GaN/m-plane. GaN in polar and semi-polar orientation shows ultraviolet emissions but yellow-emissions are only observed in GaN/c-plane sapphire. Raman spectroscopy-related oscillations show systematic variations with temperature in both GaN configurations (polar and semi-polar). This work provides a framework of characterizations for GaN with different crystal polarities. It contributes towards identifying suitable crystal growth mechanisms based on the application and requirements for doping (In, Al, etc.), crystal quality, emission, absorption, and photonic oscillations.

Research paper thumbnail of Nano-structures and luminescence mechanisms of InGaN/GaN multiple quantum well light emitting diodes

The International Conference on Electrical Engineering, 2008

A series of InGaN/GaN MQW LEDs were prepared by low pressure metalorganic chemical vapor depositi... more A series of InGaN/GaN MQW LEDs were prepared by low pressure metalorganic chemical vapor deposition (MOCVD) and studied on the nano-structural features correlated with optical properties, and luminescence emission mechanisms by analytical techniques of photoluminescence (PL), PL excitation (PLE), time resolved PL (TRPL), high-resolution (HR) X-ray diffraction (XRD) and HR transmission electron microscopy (TEM). They have shown the excellent optical and structural properties, evidenced by HRXRD, HRTEM and optical measurements. The quantum dot like structure features, unique T-behaviors of PL spectra, quantum confined Stokes effect, TRPL exploration with the variation of detecting energy and temperature and modeling analyses are studied and discussed.

Research paper thumbnail of Surface Chemical States of Heteroepitaxial Nitride Films on Sapphire by Metalorganic Chemical Vapor Deposition

International Journal of Nanoscience, 2004

Surface chemical states of GaN , AlGaN and InGaN by metalorganic chemical vapor deposition, and t... more Surface chemical states of GaN , AlGaN and InGaN by metalorganic chemical vapor deposition, and the influence of different dopants are studied with X-ray Photoelectron Spectroscopy (XPS). The results show that for most of the samples the N 1s peak can be fitted with a dominant GaN peak and a small N – H peak, while Ga 3d can be deconvoluted into three peaks from elemental Ga , GaN and Ga 2 O 3. Si -doping appears to have small influence on the surface chemical states of GaN while the influence of Mg -doping appears larger. In addition to a change in the component intensities, Mg -doping also causes the N 1s and Ga 3d peaks to broaden. The ternary AlGaN sample shows aluminum surface segregation, while the undoped InGaN shows indium surface deficiency.

Research paper thumbnail of CRYSTALLINE PHASE SEPARATION OF InGaN LAYER MATERIALS PREPARED BY METALORGANIC CHEMICAL VAPOR DEPOSITION

International Journal of Modern Physics B, Jan 20, 2002

Zn -doped InGaN thin films were epitaxied on the top of 1-2 micron thick GaN grown on sapphire by... more Zn -doped InGaN thin films were epitaxied on the top of 1-2 micron thick GaN grown on sapphire by metal organic chemical vapor deposition, and studied by a combination of high resolution X-ray diffraction (HR-XRD), micro-photoluminescence (PL) and secondary ion mass spectrometry (SIMS). HRXRD exhibits a GaN band and a single band from InGaN for samples without phase separation, but two or more InGaN bands corresponding to different x(In) for samples with phase separation. PL emissions from InGaN spread over a wider energy ranges and were modulated by the interference effects. Excitation power dependence measurements reveal 2-sets of PL emissions for samples with phase separation, but only 1-set for samples without phase separation. SIMS data showed that phase separated InGaN:Zn films possess a high Zn concentration near the InGaN-GaN interface and non-uniform distributions of In and Zn contents, which are in contrast with data from InGaN:Zn films with no In -phase separation. These interesting results are correlated to the growth process and microstructural properties.

Research paper thumbnail of Effects of CdCl2 treatment and annealing on CdS/SnO2/glass heterostructures for solar cells

Thin Solid Films, Oct 1, 2010

ABSTRACT

Research paper thumbnail of Infrared reflection investigation of ion-implanted and post-implantation-annealed epitaxially grown 6H-SiC

Surface and Interface Analysis, 2002

Multiple energy Al + and C + ions were implanted into 6H-SiC at room temperature (25 • C) and ele... more Multiple energy Al + and C + ions were implanted into 6H-SiC at room temperature (25 • C) and elevated temperature (600 • C), respectively, followed by 1550 • C annealing for 30 min. Fourier transform infrared spectroscopy was used to evaluate the optical properties in the mid-infrared range. An effective medium model, taking into account the presence of an implantation-induced amorphous phase, was developed to establish the relationship between the changes of optical properties and modification of structure. Complete amorphization in the implanted layer was evidenced for room temperature implantation but no such case occurred at elevated temperature implantation. Elimination or decrease of the amorphous phase, via 1550 • C annealing, was represented by the recovery of reflectance intensity and shape. Some structural and optical parameters, such as layer thickness and phonon damping constants of the amorphized SiC, were derived from fitting to measured data. Our work demonstrated the successful application of the Lorentz-Drude oscillator model in evaluating the lattice quality of the amorphous/crystalline SiC system.

Research paper thumbnail of Surface chemical states on 3C-SiC/Si epilayers

Applied Surface Science, Dec 1, 1994

A series of 3C-SiC/Si(100) films grown by chemical vapour deposition (CVD) with different growth ... more A series of 3C-SiC/Si(100) films grown by chemical vapour deposition (CVD) with different growth times and hence film thicknesses, are studied by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). XPS showed that the surfaces of the samples consist of Si oxides (SiO2 and SiO, where x < 2) and unreacted CH. Unreacted elemental Si is also present and its amount decreases with increasing growth time. This surface overlayer is further investigated by changing the photoelectron takeoff angle and from chemical etching studies. Compositional variations of the SiC films are also studied using SIMS. The results are discussed in terms of the three-step CVD growth process, namely, etching, buffer layer formation, and single-crystal 3C-SiC growth.

Research paper thumbnail of Indium Interdiffusion in CdTe/InSb Heterostructures Studied by Optical and Surface Analytical Techniques

Elsevier eBooks, 1994

Indium interdiffusion in MBE-grown CdTe/InSb heterostructures was studied by optical and surface ... more Indium interdiffusion in MBE-grown CdTe/InSb heterostructures was studied by optical and surface techniques of photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). A correlation between the two types of investigations was established.

Research paper thumbnail of XPS and Sims Studies of CVD-GROWN Cubic SiC Films on Si(100)

MRS Proceedings, 1994

ABSTRACTA series of CVD-grown 3C-SiC/Si(100) films of different growth times, and hence film thic... more ABSTRACTA series of CVD-grown 3C-SiC/Si(100) films of different growth times, and hence film thicknesses, are studied by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). XPS showed that the surfaces of the samples consist of Si oxides (SiO2 and SiOx where x &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 2) and unreacted C.H. Unreacted elemental Si is also present and its amount decreases with increasing growth time. This surface overlayer is further investigated by changing the photoelectron take-off angle and from chemical etching studies. Compositional variations of the SiC films are also studied using SIMS.

Research paper thumbnail of Properties of the CdTe/InSb interface studied by optical and surface analytical techniques

Physica Status Solidi A-applications and Materials Science, Jul 1, 2006

Indium interdiffusion in MBE-grown CdTe/InSb heterostructures was studied by optical and surface ... more Indium interdiffusion in MBE-grown CdTe/InSb heterostructures was studied by optical and surface techniques of photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). A correlation between the two types of investigations is established.

Research paper thumbnail of Phase separation in Zn-doped InGaN grown by metalorganic chemical vapor deposition

Materials Science in Semiconductor Processing, Feb 1, 2002

Zn-doped InGaN thin films were deposited on GaN/sapphire by metalorganic chemical vapor depositio... more Zn-doped InGaN thin films were deposited on GaN/sapphire by metalorganic chemical vapor deposition, and studied by a combination of high-resolution X-ray diffraction (HR-XRD), micro-photoluminescence (PL) and secondary ion mass spectrometry (SIMS). Indium phase separation is studied comparatively. HR-XRD exhibits a GaN band and a single band from InGaN for samples without phase separation, but two InGaN bands corresponding to different x(In) for samples with phase separation. PL excitation power dependence measurements reveal 2 sets of InGaN PL emissions for samples with phase separation, but only 1 set for samples without phase separation. SIMS data showed that phase separated InGaN:Zn films possess a high Zn concentration near the InGaN–GaN interface and non-uniform distributions of In and Zn contents, which are in contrast with data from InGaN:Zn films with no In-phase separation.

Research paper thumbnail of A Comprehensive Analysis of Porous Silicon by Surface and Optical Techniques

The surface and optical analytical techniques of XPS, AES, SIMS, FTIR and Raman were used to stud... more The surface and optical analytical techniques of XPS, AES, SIMS, FTIR and Raman were used to study porous Si membranes with visible light emission. We reveal the main components of surface layers to be SiO2 plus Si clusters and some contamination elements, and explain the anomalous Raman-temperature behaviors.

Research paper thumbnail of Raman scattering of InGaAs/InP grown by uniform radial flow epitaxy

Applied Physics Letters, Apr 13, 1992

Uniform radial flow epitaxy, a novel growth technique, has been used to grow InGaAs films on InP.... more Uniform radial flow epitaxy, a novel growth technique, has been used to grow InGaAs films on InP. Epitaxial layers above and below the critical thickness for the onset of slip were grown. We used Raman spectroscopy to characterize the quality of epitaxial layers, determine alloy composition, and measure the strain. Raman spectra from both pseudomorphic (strained) and relaxed (unstrained) InGaAs films were obtained at 300 and 80 K. The difference in the frequencies of their GaAs-like longitudinal optical phonons was used to calculate stress for the strained InGaAs/InP, leading to a direct formula for the evaluation of the layer stress.

Research paper thumbnail of Multitechnique characterization of sandwiched Si/SiGe/Si heterostructures

Z.C. Feng (1,*), H.C. Lin (1), T.R. Yang (2), R.P.G. Karunasiri (3), W. Lu (4) and W.E. Collins (... more Z.C. Feng (1,*), H.C. Lin (1), T.R. Yang (2), R.P.G. Karunasiri (3), W. Lu (4) and W.E. Collins (4). (1) Graduate Institute of Electro-Optical Engineering & Department of Electrical Engineering, National Taiwan University, Taipei, 106-17 Taiwan, ROC; (2) Department of Physics, National Taiwan Normal University, Taipei, 107 Taiwan, ROC; (3) Department of Physics, Naval Postgraduate School, Monterey, CA, USA. (4) Department of Physics, Fisk University, Nashville, TN 37208, USA. * E-mail: zcfeng@cc.ee.ntu.edu.tw

Research paper thumbnail of Far-IR reflectance spectra analysis of CdZnTe and related materials

Research paper thumbnail of Field emission properties of multi-wall carbon nanotubes

Carbon Nanotubes and Associated Devices, 2008

ABSTRACT

Research paper thumbnail of A New Method for Facial Beauty Assessment

2008 Chinese Conference on Pattern Recognition, 2008

Beauty is an abstract concept. How to quantify and evaluate beauty has always been a major concer... more Beauty is an abstract concept. How to quantify and evaluate beauty has always been a major concern among people. But few people adopt the way based on image processing and pattern recognition to assess beauty. For the first time, this paper proposed a way using computer image processing and pattern recognition for beauty assessment, and proposed a method based on

Research paper thumbnail of SiC Power Materials

Springer Series in Materials Science, 2004

The Springer Series in Materials Science covers the complete spectrum of materials physics, inclu... more The Springer Series in Materials Science covers the complete spectrum of materials physics, including fundamental principles, physical properties, materials theory and design. Recognizing the increasing importance of materials science in future device technologies, the book titles in this series reflect the state-of-the-art in understanding and controlling the structure and properties of all important classes of materials.

Research paper thumbnail of First- and second-order Raman scattering from semi-insulating4H−SiC

Physical Review B, 1999

We have measured the first-and second-order Raman spectra from semi-insulating 4H-SiC at room tem... more We have measured the first-and second-order Raman spectra from semi-insulating 4H-SiC at room temperature under nonresonant excitation. The results are compared with Raman spectra of n-type doped 4H-and 6H-SiC. The second-order spectra for both 4H-and 6H-SiC contain an acoustic branch and an optical branch, which is clearly dependent on SiC polytype. The measured two-phonon spectra are assigned by comparison with theoretical calculations.

Research paper thumbnail of Comparative investigation of high-resolution transmission electron microscopy and Fourier transform infrared spectroscopy for GaN films on sapphire substrate

Proceedings of SPIE, Nov 9, 1999

A comparative study on GaN/sapphire has been performed by transmission electron microscopy (TEM) ... more A comparative study on GaN/sapphire has been performed by transmission electron microscopy (TEM) and IR reflectance (IR). TEM observations reveal that both the undoped and Si doped GaN epilayers have large density of threading dislocations. Dislocations in ...

Research paper thumbnail of A comparative investigation of the optical properties of polar and semipolar GaN epi-films grown by metalorganic chemical vapor deposition

Semiconductor Science and Technology, Apr 22, 2022

We report on the structural and optical properties of polar gallium nitride on c-plane sapphire s... more We report on the structural and optical properties of polar gallium nitride on c-plane sapphire substrates and semi-polar (11-22) GaN films on m-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD). Polar GaN on c-plane sapphire and semi-polar GaN on m-place sapphire both show good crystal quality, luminescence, absorption, and Raman characteristics. GaN on c-place sapphire shows a high crystal quality as compared to GaN on m-plane sapphire. Surface roughness of polar GaN is lesser than semi-polar GaN. The biaxial structural stress in GaN switches from compressive to tensile as the temperature is increased. This stress-switch temperature is higher in GaN/c-plane than GaN/m-plane. GaN in polar and semi-polar orientation shows ultraviolet emissions but yellow-emissions are only observed in GaN/c-plane sapphire. Raman spectroscopy-related oscillations show systematic variations with temperature in both GaN configurations (polar and semi-polar). This work provides a framework of characterizations for GaN with different crystal polarities. It contributes towards identifying suitable crystal growth mechanisms based on the application and requirements for doping (In, Al, etc.), crystal quality, emission, absorption, and photonic oscillations.

Research paper thumbnail of Nano-structures and luminescence mechanisms of InGaN/GaN multiple quantum well light emitting diodes

The International Conference on Electrical Engineering, 2008

A series of InGaN/GaN MQW LEDs were prepared by low pressure metalorganic chemical vapor depositi... more A series of InGaN/GaN MQW LEDs were prepared by low pressure metalorganic chemical vapor deposition (MOCVD) and studied on the nano-structural features correlated with optical properties, and luminescence emission mechanisms by analytical techniques of photoluminescence (PL), PL excitation (PLE), time resolved PL (TRPL), high-resolution (HR) X-ray diffraction (XRD) and HR transmission electron microscopy (TEM). They have shown the excellent optical and structural properties, evidenced by HRXRD, HRTEM and optical measurements. The quantum dot like structure features, unique T-behaviors of PL spectra, quantum confined Stokes effect, TRPL exploration with the variation of detecting energy and temperature and modeling analyses are studied and discussed.

Research paper thumbnail of Surface Chemical States of Heteroepitaxial Nitride Films on Sapphire by Metalorganic Chemical Vapor Deposition

International Journal of Nanoscience, 2004

Surface chemical states of GaN , AlGaN and InGaN by metalorganic chemical vapor deposition, and t... more Surface chemical states of GaN , AlGaN and InGaN by metalorganic chemical vapor deposition, and the influence of different dopants are studied with X-ray Photoelectron Spectroscopy (XPS). The results show that for most of the samples the N 1s peak can be fitted with a dominant GaN peak and a small N – H peak, while Ga 3d can be deconvoluted into three peaks from elemental Ga , GaN and Ga 2 O 3. Si -doping appears to have small influence on the surface chemical states of GaN while the influence of Mg -doping appears larger. In addition to a change in the component intensities, Mg -doping also causes the N 1s and Ga 3d peaks to broaden. The ternary AlGaN sample shows aluminum surface segregation, while the undoped InGaN shows indium surface deficiency.

Research paper thumbnail of CRYSTALLINE PHASE SEPARATION OF InGaN LAYER MATERIALS PREPARED BY METALORGANIC CHEMICAL VAPOR DEPOSITION

International Journal of Modern Physics B, Jan 20, 2002

Zn -doped InGaN thin films were epitaxied on the top of 1-2 micron thick GaN grown on sapphire by... more Zn -doped InGaN thin films were epitaxied on the top of 1-2 micron thick GaN grown on sapphire by metal organic chemical vapor deposition, and studied by a combination of high resolution X-ray diffraction (HR-XRD), micro-photoluminescence (PL) and secondary ion mass spectrometry (SIMS). HRXRD exhibits a GaN band and a single band from InGaN for samples without phase separation, but two or more InGaN bands corresponding to different x(In) for samples with phase separation. PL emissions from InGaN spread over a wider energy ranges and were modulated by the interference effects. Excitation power dependence measurements reveal 2-sets of PL emissions for samples with phase separation, but only 1-set for samples without phase separation. SIMS data showed that phase separated InGaN:Zn films possess a high Zn concentration near the InGaN-GaN interface and non-uniform distributions of In and Zn contents, which are in contrast with data from InGaN:Zn films with no In -phase separation. These interesting results are correlated to the growth process and microstructural properties.

Research paper thumbnail of Effects of CdCl2 treatment and annealing on CdS/SnO2/glass heterostructures for solar cells

Thin Solid Films, Oct 1, 2010

ABSTRACT

Research paper thumbnail of Infrared reflection investigation of ion-implanted and post-implantation-annealed epitaxially grown 6H-SiC

Surface and Interface Analysis, 2002

Multiple energy Al + and C + ions were implanted into 6H-SiC at room temperature (25 • C) and ele... more Multiple energy Al + and C + ions were implanted into 6H-SiC at room temperature (25 • C) and elevated temperature (600 • C), respectively, followed by 1550 • C annealing for 30 min. Fourier transform infrared spectroscopy was used to evaluate the optical properties in the mid-infrared range. An effective medium model, taking into account the presence of an implantation-induced amorphous phase, was developed to establish the relationship between the changes of optical properties and modification of structure. Complete amorphization in the implanted layer was evidenced for room temperature implantation but no such case occurred at elevated temperature implantation. Elimination or decrease of the amorphous phase, via 1550 • C annealing, was represented by the recovery of reflectance intensity and shape. Some structural and optical parameters, such as layer thickness and phonon damping constants of the amorphized SiC, were derived from fitting to measured data. Our work demonstrated the successful application of the Lorentz-Drude oscillator model in evaluating the lattice quality of the amorphous/crystalline SiC system.

Research paper thumbnail of Surface chemical states on 3C-SiC/Si epilayers

Applied Surface Science, Dec 1, 1994

A series of 3C-SiC/Si(100) films grown by chemical vapour deposition (CVD) with different growth ... more A series of 3C-SiC/Si(100) films grown by chemical vapour deposition (CVD) with different growth times and hence film thicknesses, are studied by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). XPS showed that the surfaces of the samples consist of Si oxides (SiO2 and SiO, where x < 2) and unreacted CH. Unreacted elemental Si is also present and its amount decreases with increasing growth time. This surface overlayer is further investigated by changing the photoelectron takeoff angle and from chemical etching studies. Compositional variations of the SiC films are also studied using SIMS. The results are discussed in terms of the three-step CVD growth process, namely, etching, buffer layer formation, and single-crystal 3C-SiC growth.

Research paper thumbnail of Indium Interdiffusion in CdTe/InSb Heterostructures Studied by Optical and Surface Analytical Techniques

Elsevier eBooks, 1994

Indium interdiffusion in MBE-grown CdTe/InSb heterostructures was studied by optical and surface ... more Indium interdiffusion in MBE-grown CdTe/InSb heterostructures was studied by optical and surface techniques of photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). A correlation between the two types of investigations was established.

Research paper thumbnail of XPS and Sims Studies of CVD-GROWN Cubic SiC Films on Si(100)

MRS Proceedings, 1994

ABSTRACTA series of CVD-grown 3C-SiC/Si(100) films of different growth times, and hence film thic... more ABSTRACTA series of CVD-grown 3C-SiC/Si(100) films of different growth times, and hence film thicknesses, are studied by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). XPS showed that the surfaces of the samples consist of Si oxides (SiO2 and SiOx where x &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 2) and unreacted C.H. Unreacted elemental Si is also present and its amount decreases with increasing growth time. This surface overlayer is further investigated by changing the photoelectron take-off angle and from chemical etching studies. Compositional variations of the SiC films are also studied using SIMS.

Research paper thumbnail of Properties of the CdTe/InSb interface studied by optical and surface analytical techniques

Physica Status Solidi A-applications and Materials Science, Jul 1, 2006

Indium interdiffusion in MBE-grown CdTe/InSb heterostructures was studied by optical and surface ... more Indium interdiffusion in MBE-grown CdTe/InSb heterostructures was studied by optical and surface techniques of photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). A correlation between the two types of investigations is established.

Research paper thumbnail of Phase separation in Zn-doped InGaN grown by metalorganic chemical vapor deposition

Materials Science in Semiconductor Processing, Feb 1, 2002

Zn-doped InGaN thin films were deposited on GaN/sapphire by metalorganic chemical vapor depositio... more Zn-doped InGaN thin films were deposited on GaN/sapphire by metalorganic chemical vapor deposition, and studied by a combination of high-resolution X-ray diffraction (HR-XRD), micro-photoluminescence (PL) and secondary ion mass spectrometry (SIMS). Indium phase separation is studied comparatively. HR-XRD exhibits a GaN band and a single band from InGaN for samples without phase separation, but two InGaN bands corresponding to different x(In) for samples with phase separation. PL excitation power dependence measurements reveal 2 sets of InGaN PL emissions for samples with phase separation, but only 1 set for samples without phase separation. SIMS data showed that phase separated InGaN:Zn films possess a high Zn concentration near the InGaN–GaN interface and non-uniform distributions of In and Zn contents, which are in contrast with data from InGaN:Zn films with no In-phase separation.

Research paper thumbnail of A Comprehensive Analysis of Porous Silicon by Surface and Optical Techniques

The surface and optical analytical techniques of XPS, AES, SIMS, FTIR and Raman were used to stud... more The surface and optical analytical techniques of XPS, AES, SIMS, FTIR and Raman were used to study porous Si membranes with visible light emission. We reveal the main components of surface layers to be SiO2 plus Si clusters and some contamination elements, and explain the anomalous Raman-temperature behaviors.

Research paper thumbnail of Raman scattering of InGaAs/InP grown by uniform radial flow epitaxy

Applied Physics Letters, Apr 13, 1992

Uniform radial flow epitaxy, a novel growth technique, has been used to grow InGaAs films on InP.... more Uniform radial flow epitaxy, a novel growth technique, has been used to grow InGaAs films on InP. Epitaxial layers above and below the critical thickness for the onset of slip were grown. We used Raman spectroscopy to characterize the quality of epitaxial layers, determine alloy composition, and measure the strain. Raman spectra from both pseudomorphic (strained) and relaxed (unstrained) InGaAs films were obtained at 300 and 80 K. The difference in the frequencies of their GaAs-like longitudinal optical phonons was used to calculate stress for the strained InGaAs/InP, leading to a direct formula for the evaluation of the layer stress.

Research paper thumbnail of Multitechnique characterization of sandwiched Si/SiGe/Si heterostructures

Z.C. Feng (1,*), H.C. Lin (1), T.R. Yang (2), R.P.G. Karunasiri (3), W. Lu (4) and W.E. Collins (... more Z.C. Feng (1,*), H.C. Lin (1), T.R. Yang (2), R.P.G. Karunasiri (3), W. Lu (4) and W.E. Collins (4). (1) Graduate Institute of Electro-Optical Engineering & Department of Electrical Engineering, National Taiwan University, Taipei, 106-17 Taiwan, ROC; (2) Department of Physics, National Taiwan Normal University, Taipei, 107 Taiwan, ROC; (3) Department of Physics, Naval Postgraduate School, Monterey, CA, USA. (4) Department of Physics, Fisk University, Nashville, TN 37208, USA. * E-mail: zcfeng@cc.ee.ntu.edu.tw

Research paper thumbnail of Far-IR reflectance spectra analysis of CdZnTe and related materials

Research paper thumbnail of Field emission properties of multi-wall carbon nanotubes

Carbon Nanotubes and Associated Devices, 2008

ABSTRACT

Research paper thumbnail of A New Method for Facial Beauty Assessment

2008 Chinese Conference on Pattern Recognition, 2008

Beauty is an abstract concept. How to quantify and evaluate beauty has always been a major concer... more Beauty is an abstract concept. How to quantify and evaluate beauty has always been a major concern among people. But few people adopt the way based on image processing and pattern recognition to assess beauty. For the first time, this paper proposed a way using computer image processing and pattern recognition for beauty assessment, and proposed a method based on

Research paper thumbnail of SiC Power Materials

Springer Series in Materials Science, 2004

The Springer Series in Materials Science covers the complete spectrum of materials physics, inclu... more The Springer Series in Materials Science covers the complete spectrum of materials physics, including fundamental principles, physical properties, materials theory and design. Recognizing the increasing importance of materials science in future device technologies, the book titles in this series reflect the state-of-the-art in understanding and controlling the structure and properties of all important classes of materials.

Research paper thumbnail of First- and second-order Raman scattering from semi-insulating4H−SiC

Physical Review B, 1999

We have measured the first-and second-order Raman spectra from semi-insulating 4H-SiC at room tem... more We have measured the first-and second-order Raman spectra from semi-insulating 4H-SiC at room temperature under nonresonant excitation. The results are compared with Raman spectra of n-type doped 4H-and 6H-SiC. The second-order spectra for both 4H-and 6H-SiC contain an acoustic branch and an optical branch, which is clearly dependent on SiC polytype. The measured two-phonon spectra are assigned by comparison with theoretical calculations.