Solid State Physics Laboratory

About: Solid State Physics Laboratory is a facility organization based out in Delhi, India. It is known for research contribution in the topics: Quantum dot & Dielectric. The organization has 1754 authors who have published 2597 publications receiving 50601 citations.

Comparative study of Au and Ni/Au gated AlGaN/GaN high electron mobility transistors

Abstract: This paper presents the electrical comparison of Au and Ni/Au gated HEMT devices and diodes. Au Schottky diodes on an AlGaN/GaN heterostructure exhibit better electrical performance in comparison to conventional Ni/Au diodes with an improved Schottky barrier height (SBH) and lower reverse leakage current. The SBH extracted from I-V for Au and Ni/Au is 1.29 eV and 0.74 eV, respectively. Au Schottky contacts on GaN have a better ideality factor of 1.55 than Ni, which is 1.61. Capacitance-voltage measurement revealed a positive shift in threshold voltage in the case of Au diodes with a reduced capacitance value with respect to Ni/Au diodes. This decrease in threshold and capacitance indicates a decrease in the 2DEG carrier concentration. The decrease in the 2DEG carrier concentration is consistent with three terminal device measurements. Despite a small decrease in drain current (8%), the Au gated HEMT devices have shown an improved subthreshold slope (13%) and nearly 4 order improvement in the ION/IOFF ratio than Ni/Au gated HEMTs. Pulse IV characterization has indicated that gate lag and drain lag have no major changes with respect to gate metal, whereas current collapse increases for high work function metals.

Preparation of 4:55:45 samarium doped PZT films by sol-gel technique and their characterization

Abstract: Thin ferroelectric films of samarium doped PZT (4:55:45) were prepared by sol-gel technique on ITO coated corning 7059 glass. Characterization of these films by X-ray diffraction and scanning electron microscopy shows that the films are formed perovskite tetragonal phase with submicron crystallite size. Charge field hysteresis, dielectric relaxation and pyroelectric studies were carried on these films. It is concluded that these films with their high pyroelectric coefficient ∼45 nC cm−2 K−1 and low dielectric constant ∼230 will find application as pyroelectric sensor elements.

Structural and dielectric properties of Fe-substituted BST thin films grown by laser ablation

Abstract: BST thin films are grown by pulsed laser deposition technique at different temperatures and different oxygen deposition pressures. X-ray diffraction studies confirm the perovskite phase of the films. From the ɛ′–V characteristic tunability is calculated and the films grown at lower oxygen deposition pressure is found have higher tunability which is explained in terms of stress developed in the film and oxygen vacancies formed during deposition. The ɛ′–V variation is explained in terms of Devonshire's phenomenological theory.

Optical absorption of ZnGa2Se

Abstract: Single crystals of ${\mathrm{ZnGa}}_{2}$${\mathrm{Se}}_{4}$:${\mathrm{Co}}^{2+}$ were grown by the chemical transport reaction method. The optical absorption of single crystals was investigated in the temperature range 20\char21{}300 K. The optical-absorption peaks due to the transition $^{4}\mathrm{A}_{2}$${(}^{4}$F)${\ensuremath{\rightarrow}}^{4}$${\mathrm{T}}_{1}$${(}^{4}$P), $^{4}\mathrm{A}_{2}$${(}^{4}$F)${\ensuremath{\rightarrow}}^{4}$${\mathrm{T}}_{1}$${(}^{4}$F), and $^{4}\mathrm{A}_{2}$${(}^{4}$F)${\ensuremath{\rightarrow}}^{4}$${\mathrm{T}}_{2}$${(}^{4}$F) of the ${\mathrm{Co}}^{2+}$ ion that has entered the substitutional tetrahedral sites appeared at 12 830, 6221, and 4000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ at 289 K. The crystal-field parameter and the Racah parameter were given by Dq=400 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and B=469 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, respectively. The transition $^{4}\mathrm{A}_{2}$${(}^{4}$F)${\ensuremath{\rightarrow}}^{4}$${\mathrm{T}}_{1}$${(}^{4}$P) split into a triplet state by first-order spin-orbit\char21{}coupling effects in the temperature range 55\char21{}289 K, and the ${\ensuremath{\Gamma}}_{8}$+${\ensuremath{\Gamma}}_{7}$ level split into ${\ensuremath{\Gamma}}_{8}$ and ${\ensuremath{\Gamma}}_{7}$ levels by second-order spin-orbit\char21{}coupling effects of ${\mathrm{Co}}^{2+}$ ions in the low-temperature range below 55 K. The spin-orbit\char21{}coupling parameter was found to be \ensuremath{\lambda}=-363 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$.

X-ray diffraction measurements on liquid iodine and some dilute mixtures of KI in I2

Abstract: Using X-ray diffraction we have determined the structure factor of pure iodine and of a number of dilute mixtures of KI in I2. We show that these liquids exhibit short-range orientational order, adjacent molecules being orient- ed more or less parallel. The intramolecular bond length in pure liquid iodine is 2·70±0·01 A, intermediate between the bond lengths of gaseous and solid iodine. Upon addition of KI the bond length increases, while the distances to atoms in the second and third shell decrease. These effects are related to recent high-pressure diffraction measurements on solid iodine.