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Lothar Ley

Publications and source records attributed to Lothar Ley.

5 recordsLinked to original sources
arXiv2026

High-field Magnetotransport Studies of Surface Conducting Diamonds

The observation of strong and tunable spin-orbit interaction (SOI) in surface conducting diamond opens up a new avenue for building diamond-based spintronics. Herein we provide a comprehensive method to analyze the magnetotransport behavior of surface conducting hydrogen-terminated diamond (H-diamond) Hall bar devices and Al/Al2O3/V2O5/H-diamond MOSFETs, respectively. By adopting a significantly improved theoretical magneto transport model, the reduced magnetoconductance can be accurately explained both within and outside the quantum diffusive regime. The model is valid for all doping strategies of surface conducting diamond tested. From this analysis, we find that the orbital magnetoresistance, a classical effect distinct from the SOI, dominates the magnetotransport in surface conducting diamond at high magnetic fields. Furthermore, local hole mobilities as high as 1000 ~ 3000 cm2/Vs have been observed in this work, indicating the possibility of diamond-based electronics with ultra-high hole mobilities at cryogenic temperatures.

cond-mat.mtrl-sci↗
arXiv2020

Attosecond-fast internal photoemission

The photoelectric effect has a sister process relevant in optoelectronics called internal photoemission. Here an electron is photoemitted from a metal into a semiconductor. While the photoelectric effect takes place within less than 100 attoseconds, the attosecond time scale has so far not been measured for internal photoemission. Based on the new method CHArge transfer time MEasurement via Laser pulse duration-dependent saturation fluEnce determinatiON, CHAMELEON, we show that the atomically thin semi-metal graphene coupled to bulk silicon carbide, forming a Schottky junction, allows charge transfer times as fast as (300 $\pm$ 200) attoseconds. These results are supported by a simple quantum mechanical model simulation. With the obtained cut-off bandwidth of 3.3 PHz for the charge transfer rate, this semimetal-semiconductor interface represents the first functional solid-state interface offering the speed and design space required for future light-wave signal processing.

physics.app-ph↗
arXiv2015

Extremely high negative electron affinity of diamond via magnesium adsorption

We report large negative electron affinity (NEA) on diamond (100) using magnesium adsorption on a previously oxygen-terminated surface. The measured NEA is up to $(-2.01\pm0.05)$ eV, the largest reported negative electron affinity to date. Despite the expected close relationship between the surface chemistry of Mg and Li species on oxygen-terminated diamond, we observe differences in the adsorption properties between the two. Most importantly, a high-temperature annealing step is not required to activate the Mg-adsorbed surface to a state of negative electron affinity. Diamond surfaces prepared by this procedure continue to possess negative electron affinity after exposure to high temperatures, air and even immersion in water.

cond-mat.mtrl-sci↗
arXiv2008

Atmospheric pressure graphitization of SiC(0001)- A route towards wafer-size graphene layers

We have investigated epitaxial graphene films grown on SiC(0001) by annealing in an atmosphere of Ar instead of vacuum. Using AFM and LEEM we observe a significantly improved surface morphology and graphene domain size. Hall measurements on monolayer graphene films show a carrier mobility of around 1000 cm^2/Vs at room temperature and 2000 cm^2/Vs at 27K. The growth process introduced here establishes the synthesis of graphene films on a technologically viable basis.

cond-mat.mtrl-sci↗