Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDirect measurement and the diameter-dependence of minority carrier diffusion length in individual ZnO nanowires
90
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
This paper has been withdrawn by the author.
rate research
Read More
We report measurements of electronic, thermoelectric, and galvanomagnetic properties of individual single crystal antimony telluride (Sb2Te3) nanowires with diameters in the range of 20-100 nm. Temperature dependent resistivity and thermoelectric power (TEP) measurements indicate hole dominant diffusive thermoelectric generation, with an enhancement of the TEP for smaller diameter wires up to 110 uV/K at T = 300 K. We measure the magnetoresistance, in magnetic fields both parallel and perpendicular to the nanowire [110] axis, where strong anisotropic positive magnetoresistance behavior was observed.
Nanowires (NWs) with their quasi-one-dimensionality often present different structural and opto-electronic properties than their thin-film counterparts. The thinner they are the larger these differences are, in particular in the carrier-phonon scattering and thermal conductivity. In this work, we present femtosecond transient absorbance measurements on GaAs0.8P0.2 NWs of two different diameters, 36 and 51 nm. The results show that thinner NWs sustain the hot-carriers at a higher temperature for longer times than thicker NWs. We explain the observation suggesting that in thinner NWs, the build-up of a hot-phonon bottleneck is easier than in thicker NWs because of the increased phonon scattering at the NW sidewalls which facilitates the build-up of a large phonon density. The large number of optical phonons emitted during the carrier relaxation processes generate a non-equilibrium population of acoustic phonons that propagates less efficiently in thin NWs. This makes the possible acoustic-to-optical phonon up-conversion process easier, which prolongs the LO phonon lifetime resulting in the slowdown of the carrier cooling. The important observation that the carrier temperature in thin NWs is higher than in thick NWs already at the beginning of the hot carrier regime suggests that the phonon-mediated scattering processes in the non-thermal regime play a major role at least for the carrier densities investigated here (8x1018-4x1019 cm-3). Our results also suggest that the boundary scattering of phonons at crystal defects is negligible compared to the surface scattering at the NW sidewalls.
We have studied the spin transport and the spin Hall effect as a function of temperature for platinum (Pt) and gold (Au) in lateral spin valve structures. First, by using the spin absorption technique, we extract the spin diffusion length of Pt and Au. Secondly, using the same devices, we have measured the spin Hall conductivity and analyzed its evolution with temperature to identify the dominant scattering mechanisms behind the spin Hall effect. This analysis confirms that the intrinsic mechanism dominates in Pt whereas extrinsic effects are more relevant in Au. Moreover, we identify and quantify the phonon-induced skew scattering. We show that this contribution to skew scattering becomes relevant in metals such as Au, with a low residual resistivity.
We have determined the finite temperature coherence length of edge states in the Integer Quantum Hall Effect (IQHE) regime. This was realized by measuring the visibility of electronic Mach-Zehnder interferometers of different sizes, at filling factor 2. The visibility shows an exponential decay with the temperature. The characteristic temperature scale is found inversely proportional to the length of the interferometer arm, allowing to define a coherence length $l_phi$. The variations of $l_phi$ with magnetic field are the same for all samples, with a maximum located at the upper end of the quantum hall plateau. Our results provide the first accurate determination of $l_phi$ in the quantum Hall regime.
We investigated the effect of an external magnetic field on the diffusive spin transport by magnons in the magnetic insulator yttrium iron garnet (YIG), using a non-local magnon transport measurement geometry. We observed a decrease in magnon spin diffusion length $lambda_m$ for increasing field strengths, where $lambda_m$ is reduced from 9.6$pm1.2$ $mu$m at 10 mT to 4.2$pm0.6$ $mu$m at 3.5 T at room temperature. In addition, we find that there must be at least one additional transport parameter that depends on the external magnetic field. Our results do not allow us to unambiguously determine whether this is the magnon equilibrium density or the magnon diffusion constant. These results are significant for experiments in the more conventional longitudinal spin Seebeck geometry, since the magnon spin diffusion length sets the length scale for the spin Seebeck effect as well and is relevant for its understanding.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
