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.

Spin polarization, dephasing, and photoinduced spin diffusion in (110)-grown two-dimensional electron systems

Abstract: We study the optically induced spin polarization, spin dephasing, and diffusion in several high-mobility two-dimensional electron systems, which are embedded in GaAs quantum wells grown on (110)-oriented substrates. The experimental techniques comprise a two-beam magneto-optical spectroscopy system and polarization-resolved photoluminescence. Under weak excitation conditions at liquid-helium temperatures, we observe spin lifetimes above 100 ns in one of our samples, which are reduced with increasing excitation density due to additional, hole-mediated, spin dephasing. The spin dynamic is strongly influenced by the carrier density and the ionization of remote donors, which can be controlled by temperature and above-barrier illumination. The absolute value of the average electron spin polarization in the samples is directly observable in the circular polarization of photoluminescence collected under circularly polarized excitation and reaches values of about 5%. Spin diffusion is studied by varying the distance between pump and probe beams in microspectroscopy experiments. We observe diffusion lengths above 100 $\ensuremath{\mu}$m and, at high excitation intensity, a nonmonotonic dependence of the spin polarization on the pump-probe distance.

Impact of post deposition annealing in N2 ambient on structural properties of nanocrystalline hafnium oxide thin film

Abstract: In the present work, HfO2 thin film (100 nm) has been deposited by sputtering technique and annealed at various temperatures ranging from 400 to 1000 °C (in step of 200 °C) in O2 ambient for 10 min. The samples have been characterized using XRD, FTIR, EDAX, AFM and Laser Ellipsometer. The impact of annealing temperatures in O2 ambient on structural properties such as crystallite size, phase, orientation, stress have been studied using XRD. The Hf–O phonon peaks in the infrared absorption spectrum are detected at 512, 412 cm−1. The stretching vibration modes at 720 and 748 cm−1 correspond to HfO2. AFM data show mean grain size in the range of 38–67 nm. The film reveals variation in structural properties, which appears to be responsible for variation in oxygen percentage, refractive index (1.96–2.01) at 632 nm wavelength and roughness (6.13–16.40 nm). Annealing temperature as well as ambient condition has significant effects on stress, crystal size and thus the arrangement of atoms. For good quality film, annealing temperature larger than 600 °C is desired.

Improvement of the transport properties of a high-mobility electron system by intentional parallel conduction

Abstract: We present a gating scheme to separate even strong parallel conduction from the magneto-transport signatures and properties of a two-dimensional electron system. By varying the electron density in the parallel conducting layer, we can study the impact of mobile charge carriers in the vicinity of the dopant layer on the properties of the two-dimensional electron system. It is found that the parallel conducting layer is indeed capable to screen the remote ionized impurity potential fluctuations responsible for the fragility of fractional quantum Hall states.