Ahmad Hadi Ali

Post-Annealing Effects on ITO Thin Films RF Sputtered at Different Thicknesses on Si and Glass

We report on electrical, optical and surface morphological characteristics of indium tin oxide (ITO) thin films. The ITO was deposited by radio frequency (RF) magnetron sputtering on Si and glass substrates at different thicknesses of 125 nm and 239 nm. Post-annealing treatment was conducted on the samples at temperature of 500°C and 600°C. From Hall Effect measurement, the lowest resistivity was measured as 4.4 × 10-4 Ωcm and 4.5 × 10-4 Ωcm corresponding to the 239 nm and 125 nm ITO sample, respectively, after post-annealed at 600°C. Using UV-Vis spectrophotometer, the highest transmittance of ~84% at 470 nm was observed with respect to the 125 nm ITO thin films after post-annealed at 500°C. Furthermore, the 500°C post-annealed 125 nm thin film shows highest carrier concentrations of more than 1021 cm-3 and smoothest surface morphology of 0.5 nm root-mean-square, RMS. It is clearly shown that post-annealing treatment on ITO thin films is able to enhance the electrical and optical transmittance properties as compared to the as deposited films.

Structural properties of InGaN-based light-emitting diode epitaxial growth on Si (111) with AlN/InGaN buffer layer

This paper reports on structural characterization of InGaN-based light-emitting diode (LED) with AlN/InGaN buffer layer, AlN/GaN multi layer (ML) intermediate layer and AlGaN/GaN strain layer superlattices (SLS). The LED was epitaxially grown on Si (111) by metal organic chemical vapor deposition (MOCVD) that comprises of InGaN/InGaN multi quantum-wells (MQWs) active layer sandwiched between InGaN under-layer and over-layer. Phase analysis (PA) 2Theta-scan x-ray diffraction (XRD) proved the existence of single crystal GaN (0002) and (0004) at 34.5° and 73.2°, respectively. X-ray rocking curve (XRC) phi-scan showed six-fold symmetric diffraction peaks confirming the wurtzite GaN structures with consistent angular gaps of ~60°. The red shift of E2 (high) GaN with respect to the standard value of strain-free bulk GaN denotes the presence of compressive strain in the epilayer. Surface morphology by atomic force microscope (AFM) shows a smooth surface with low RMS roughness value, thus proved a good quality of InGaN-based LED structure grown on Si.

Compositional and Structural Characterization of Heterostructure InGaN-Based Light-Emitting Diode by High Resolution X-Ray Diffraction

This paper focuses on the compositional and structural characterization of InGaN-based light-emitting diode (LED) using high resolution x-ray diffraction (HRXRD) system. The LED was epitaxially grown on Si (111) substrate that comprises of In0.11Ga0.89N multi-quantum-well (MQW) active layer. Phase analysis 2θ-scan proved the composition of GaN (0002) and (0004) at 34.63o and 72.98o, respectively. Rocking curve φ-scan showed six significant peaks of the hexagonal GaN structures with consistent angular gaps of ~60o. From x-ray rocking curve (XRC) ω-scan, screw and mix dislocation density is found as 2.85 × 109 cm-2, while pure edge dislocation density is found as 2.23 × 1011 cm-2.

Physical and chemical changes of polystyrene nanospheres irradiated with laser

It has been reported that polymer resist such as PMMA (Polymethyl methacrylate) which is a well known and commonly used polymer resist for fabrication of electronic devices can show zwitter characteristic due to over exposure of electron beam [1]. They tend to change their molecular structure to either become negative or positive resist corresponded to irradiation doses. These characteristic was due to crosslinking and scissors of the PMMA molecular structures, but till now the understanding of crosslinking and scissors of the polymer resist molecular structure due to electron beam exposure were still unknown to researchers [2–5].