Roslan Hashim

Optical absorption and photoluminescence studies of gold nanoparticles deposited on porous silicon.

We present an investigation on a coupled system consists of gold nanoparticles and silicon nanocrystals. Gold nanoparticles (AuNPs) embedded into porous silicon (PSi) were prepared using the electrochemical deposition method. Scanning electron microscope images and energy-dispersive X-ray results indicated that the growth of AuNPs on PSi varies with current density. X-ray diffraction analysis showed the presence of cubic gold phases with crystallite sizes around 40 to 58 nm. Size dependence on the plasmon absorption was studied from nanoparticles with various sizes. Comparison with the reference sample, PSi without AuNP deposition, showed a significant blueshift with decreasing AuNP size which was explained in terms of optical coupling between PSi and AuNPs within the pores featuring localized plasmon resonances.

Fabrication and Characterization of Planar Dipole Antenna Integrated with GaAs Based-Schottky Diode for On-chip Electronic Device Application

The design and RF characteristics of planar dipole antennas facilitated with coplanar waveguide (CPW) structure on semi-insulated GaAs are performed and confirmed to work in super high frequency (SHF) range. As expected, the fundamental resonant frequency shifts to higher frequency when the length of antenna decreases. Interestingly, the resonant frequencies of antenna are almost unchanged with the variation of antenna width and metal thickness. It is shown experimentally that return loss down to −54 dB with a metal thickness of 50 nm is obtainable. Preliminary investigation on design, fabrication, and DC and RF characteristics of the integrated device (planar dipole antenna + Schottky diode) on AlGaAs/GaAs HEMT structure is presented. From the preliminary direct irradiation experiments using the integrated device, the Schottky diode is not turned on due to weak reception of RF signal by dipole antenna. Further extensive considerations on the polarization of irradiation etc. need to be carried out in order to improve the signal reception. These preliminary results provide a new breakthrough for on-chip electronic device application in nanosystems.

Silver nanoclusters formation by using thermal annealing on porous GaAs

Recent advances in nanotechnology that allow metal structures to be built at a nanometer scale have expedited the implementation of the surface-plasmon (SP) resonance effect which effect concentrates and guides light into structures that are smaller than the wavelength of the propagating light. The numerous researchers have successfully shown that the wavelength at which the extinction reaches its maximum can be selectively tuned by adjusting the metal particle size, shape, volume fraction, interparticle distance, and the dielectric properties of the metal as well as that of the surrounding medium [1].

Thermally treated Ge crystallites embedded inside PS with Si capping layer for potential photonics application

Germanium is an interesting group IV semiconductor for its high carrier mobility and is considered for the application in high speed electronics. It also displays unique optical properties at the nanoscale and holds potential for the application in photonics [1]. Many techniques have been employed to grow Ge nanostructures such as self-assembled growth of Ge nanometer islands in highly strained system using sophisticated Molecular Beam Epitaxy (MBE)[2] and Low Pressure Chemical Vapor Deposition(LPCVD) techniques [3]. Huang et al [4] used porous silicon (PS) as the substrate for Ge quantum dots formation. The Ge was deposited by using UHV-CVD technique. They successfully showed potential PS as a patterned substrate for the Ge dot formation which showed emission at the infrared region.

Nanostructures of III-V semiconductor for photonic, electronic, and sensing applications back to basics

With the advancement of technology, the semiconductor materials are fabricated with ever shrinking size in order to reduce space and weight while at the same time benefiting from the improved performance such as high speed and low operating power. Recently found phenomena called, quantum confinement (QC) effects related to semiconductor material reaching the size in nanometer scale, only added to the excitement among researchers in this field around the world. Among notable effects of QC in nano-sized semiconductor is the enlargement of the bandgap due to the folding of the Brillouin zone. A few notable techniques that have been developed along this line are Metal Oxide Chemical Vapor Deposition (MOCVD), Molecular Beam Epitaxy (MBE), and Liquid Phase Chemical Vapor Deposition to name but a few. However these machines are very expensive to operate especially for large scale production. This obstacle has prompted researchers to find other alternatives for cheaper production cost but trying to maintain the quality of the grown nanostructures for high performance devices. Those techniques are the ones which had been used before the QC effects are found. In this talk we are revisiting one of the low cost conventional techniques to grow high quality III-V nanostructure on Si substrate, that is electrochemical etching and deposition. This technique relies on the type of electrolyte, electrical current, temperature, time and ambient light. The quality of the grown layers is studied using SEM, PL, Raman and XRD Spectroscopy. The potential application of the grown layers in light emission, light detection, and gas sensing is also discussed.