PA-MBE GaN-Based Optoelectronics on Silicon Substrates

Dalam penyelidikan ini, epitaksi alur molekul berbantukan plasma nitrogen frekuensi radio (RF) digunakan untuk menumbuhkan bahan galium nitrid (GaN) di atas substrat Si(111) dengan penggunaan aluminium nitrid (AlN) yang ditumbuhkan pada suhu tinggi sebagai lapisan penimbal. In this project, radio-frequency (RF) nitrogen plasma-assisted molecular beam epitaxy (PA-MBE) technique was used to grow GaN-based layers on Si(111) substrate using high temperature grown AlN as buffer layer

Study of nanostructured W03.

In this project we have investigated and successfully revealed another method to produce this nanostructured tungsten trioxide (W03) film of several microns length using electrochemically method and nitric acid as the solution. We have 5 samples that we set the solution concentricity to be varies from 0.5 M to 2.5 M in order to find the best method among those solution concentricity. A platelet- like or stripe-like crystals with the length of 20 to 500nm were obtained after anodization of tungsten foils. All test result covers on physical, morphological, vibrational modes and structural analysis has proved that all 5 samples was able to formed a nanostructure tungsten oxide by the anodization process at a constant 60 Volts of power supply and annealed at 500°C for 2 hours

High Sensitivity of Porous Si-Doped GaN MSM Photodetector using Thermally Untreated Platinum Contact

this work. we report the formation of porous Si-doped GaN films under a novel alternating current (sine-wave a.c. (50 Hz)) photo-assisted electrochemical (ACPEC) etching conditions. The ACPEC formed porous GaN with excellent structural and surface morphology. Field emission scanning electron microscope (FESEM), atomic force microscopy (AFM), photoluminescence (PL), Raman spectra and high resolution X-ray diffraction (HR-XRD) phi-scan and rocking curves measurements evidenced important features of the pore morphology, nanostructures and optical properties. According to the FESEM micrographs, the GaN thin films exhibit a homogeneous nanoporous structures with spatial nano-flakes arrangement. The AFM measurements revealed an increase in the surface roughness induced by porosification. The porous layer exhibited a substantial PL intensity enhancement with red-shifted band-edge PL peaks associated with the relaxation of compressive stress. The shift of E2(high) to the lower frequency in Raman spectra of the porous GaN films further confirms such a stress relaxation. X-ray diffraction phi-scan showed that porous GaN sample maintained the epitaxial features. Thermally untreated platinum (Pt) finger contact was deposited on the porous GaN to form MSM photodetector. The current-voltage (I-V) measurements indicated that the devices were highly sensitive to ambient light. The photocurrent rise and decay times were investigated under 365 nm chopped light and at bias voltages of 1, 3 and 5 V

Chemical bonding states and solar selective characteristics of unbalanced magnetron sputtered TixM1-x-yNy films

Transition metal nitride TixM1-x-yNy (M = Al or AlSi) based thin films are evaluated as solar selective surfaces by correlating their spectral selective features with their crystal structure and chemical bonding state including mechanical strength. Ti0.5N0.5, Ti0.25Al0.25N0.5, and Ti0.25Al0.2Si0.05N0.5 films were synthesized on AISI M2 steel substrates via closed field unbalanced magnetron sputtering technology. These were investigated using XRD, SEM, XPS, UV-Vis, FTIR and nanoindentation techniques. Analysis of the optical properties showed the solar absorptance, in the visible range, of the TixM1-x-yNy films improved significantly from 51% to 81% with AlSi-doping and an increase of solar absorptance of up to 66% was recorded from films doped with Al. Moreover, the Al doping can reduce the thermal emittance in the infrared range from 6.06% to 5.11%, whereas doping with AlSi reduces the emittance to ca. 3.58%. The highest solar selectivity of 22.63 was achieved with TiAlSiN films. Mechanical studies showed enhanced hardness by ∼32%; enhanced yield strength by ∼16% and enhanced plastic deformation by ∼110% of Al and AlSi doped TiN matrix. © 2016 The Royal Society of Chemistry

Design of high-speed clock and data recovery circuits

This article describes the various architectures for a high-speed clock and data recovery (CDR) circuit. Following a brief introduction of clock and data recovery circuit, a phase detection circuit, one of the most critical blocks in a CDR that determines not only the performance but also the CDR architecture, is addressed. The descriptions start with the most basic XOR logic up to the phase-frequency detector circuit. Trade-offs of each of the phase detectors are outlined. Two types of dual loop CDR architecture are briefly introduced. Finally, full-rate and half rate CDR architectures are described