arXiv subjects

Sam Saiter

Publications and source records attributed to Sam Saiter.

3 recordsLinked to original sources

arXiv2026

Magnetotransport Measurements on Isolated Polycrystalline Grains of Type-II Silicon Clathrate

The first low-temperature electronic transport characterization of individual polycrystalline grains of type-II silicon clathrate (Na$_x$Si$_{136}$, $x \ll 1$), isolated using microfabrication techniques, is reported. Structural characterization via Raman spectroscopy confirms that the isolated grains are largely devoid of amorphous silicon (a-Si). Temperature-dependent resistivity reveals multiple conduction regimes, including thermally activated freeze-out behavior and a transition to low-activation-energy transport at cryogenic temperatures, consistent with hopping conduction mechanisms. Hall measurements from 290 K to 3.5 K yield carrier concentration and mobility trends that correlate with the extracted activation energies, verifying $n$-type conduction. Additionally, gate-dependent conductivity measurements demonstrate electrostatic tunability at room temperature. Collectively, these results establish the magnetotransport parameters of single, isolated grains of type-II silicon clathrate and demonstrate the potential of this material for future quantum and optoelectronic devices.

cond-mat.mtrl-sci↗

arXiv2026

Morphology control and low-temperature magnetotransport in chiral 2D perovskite R-(MBA)$_2$PbI$_4$

Two-dimensional chiral hybrid perovskites, such as R/S-(MBA)\textsubscript{2}PbI\textsubscript{4}, are leading candidates for realizing and studying chirality-dependent charge and spin transport. However, their prohibitive in-plane resistance has precluded the electrical characterization. Here, we overcome this bottleneck by engineering the thin-film morphology of the chiral perovskite $R\text{-(MBA)}_2\text{PbI}_4$, enabling the first robust lateral device integration. In Hall-bar geometries, we demonstrate Hall measurements under dark conditions, unambiguously identifying p-type conduction with a Hall mobility of $\sim 0.2 \text{cm}^2 \text{V}^{-1} \text{s}^{-1}$ and a carrier density of $\sim 3\times10^{14} \text{ cm}^{-2}$, parameters previously inaccessible in this class of materials. Furthermore, we observe enhanced magnetoresistance along transport paths crossing grain boundaries, highlighting the strong influence of morphology on in-plane transport. This work demonstrates in-plane magnetotransport, enabling future investigations of the fundamental mechanisms of chirality-induced spin selectivity (CISS) and accelerating the integration of chiral materials into functional spintronic devices.

cond-mat.mtrl-sci↗

arXiv2025

An optically enhanced crystalline silicon allotrope: hydrogen passivated type II silicon clathrate

While Si clathrates have been explored as promising direct bandgap semiconductors, their practical optoelectronic performance has been limited by high doping levels and structural defects. Hydrogen has long been used to improve the optoelectronic quality of conventional Si, yet its role in clathrate structures remains unexplored. In this study, we demonstrate that hydrogen (deuterium) can be incorporated into type II Si clathrate framework using remote plasma treatment. This process leads to the formation of NaD and SiD complexes, which significantly reduce both the Na donor density and dangling bond defects. Electron paramagnetic resonance confirms nearly a tenfold decrease in Na-related donor states, resulting in the lowest doping level reported in Si clathrates to date. Following passivation, the integrated photoluminescence intensity increases by a factor of 40, accompanied by a blue shift of the main emission peak, consistent with a transition closer to the intrinsic band edge. A new emission peak at 930 nm, attributed to hydrogen-related recombination centers, also appears. These improvements remain stable up to 400 oC. Altogether, this work establishes hydrogen passivation as a viable strategy for enhancing light emission in Si clathrates and opens a new pathway toward their application in Si-based light-emitting diodes and other direct-bandgap optoelectronic devices.

cond-mat.mtrl-sci↗