arXiv subjects

Daniel R. Lenski

Publications and source records attributed to Daniel R. Lenski.

2 recordsLinked to original sources

arXiv2011

Raman and optical characterization of multilayer turbostratic graphene grown via chemical vapor deposition

We synthesize large-area graphene via atmospheric-pressure (AP) chemical vapor deposition (CVD) on copper, and transfer to SiO2 wafers. In contrast to low-pressure (LP) CVD on copper, optical contrast and atomic force microscopy measurements show AP-CVD graphene contains significant multi-layer areas. Raman spectroscopy always shows a single Lorentzian 2D peak, however systematic differences are observed in the 2D peak energy, width, and intensity for single- and multi-layer regions. We conclude that graphene multi-layers grown by AP-CVD on Cu are rotationally disordered.

cond-mat.mtrl-sci↗

arXiv2009

Frequency-dependent complex conductivity of an organic thin-film transistor

We measure the complex impedance between source/drain electrodes and the gate electrode of a pentacene thin-film transistor (TFT) at frequencies 50 Hz < omega/2pi < 20 kHz. Modeling the TFT as a distributed RC network (RC transmission line), we find that the data cannot be explained by a model including only a real, frequency-independent sheet conductivity. Instead, we use the RC transmission line model to extract the frequency-dependent complex sheet conductivity sigma(omega) = sigma'(omega) + jsigma"(omega) of the pentacene film. At high frequencies, sigma(omega) increases with frequency, sigma'(omega) and sigma"(omega) become similar in magnitude, and the on/off ratio is significantly reduced.

cond-mat.mtrl-sci↗