arXiv subjects

D. P. Chu

Publications and source records attributed to D. P. Chu.

5 recordsLinked to original sources

arXiv2011

Ink-Jet Printed Graphene Electronics

We demonstrate ink-jet printing as a viable method for large area fabrication of graphene devices. We produce a graphene-based ink by liquid phase exfoliation of graphite in N-Methylpyrrolidone. We use it to print thin-film transistors, with mobilities up to~95cm^2V^(-1)s(-1), as well as transparent and conductive patterns, with~80 % transmittance and~30kOhm/sq sheet resistance. This paves the way to all-printed, flexible and transparent graphene devices on arbitrary substrates

cond-mat.mtrl-sci↗

arXiv2001

Temperature dependence of the ohmic conductivity and activation energy of Pb1+y(Zr0.3Ti0.7)O3 thin films

The ohmic conductivity of the sol-gel derived Pb1+y(Zr0.3Ti0.7)O3 thin films (with the excess lead y=0.0 to 0.4) are investigated using low frequency small signal alternate current (AC) and direct current (DC) methods. Its temperature dependence shows two activation energies of 0.26 and 0.12 eV depending on temperature range and excess Pb levels. The former is associated with Pb3+ acceptor centers, while the latter could be due to a different defect level yet to be identified.

cond-mat.mtrl-sci↗

arXiv1997

Dopant Spatial Distributions: Sample Independent Response Function And Maximum Entropy Reconstruction

We demonstrate the use of maximum entropy based deconvolution to reconstruct boron spatial distribution from the secondary ion mass spectrometry (SIMS) depth profiles on a system of variously spaced boron $δ$-layers grown in silicon. Sample independent response functions are obtained using a new method which reduces the danger of incorporating real sample behaviour in the response. Although the original profiles of different primary ion energies appear quite differently, the reconstructed distributions agree well with each other. The depth resolution in the reconstructed data is increased significantly and segregation of boron at the near surface side of the $δ$-layers is clearly shown.

cond-mat.mtrl-sci↗

arXiv1996

Characterization of the Noise in Secondary Ion Mass Spectrometry Depth Profiles

The noise in the depth profiles of secondary ion mass spectrometry (SIMS) is studied using different samples under various experimental conditions. Despite the noise contributions from various parts of the dynamic SIMS process, its overall character agrees very well with the Poissonian rather than the Gaussian distribution in all circumstances. The Poissonian relation between the measured mean-square error (MSE) and mean can be used to describe our data in the range of four orders. The departure from this relation at high counts is analyzed and found to be due to the saturation of the channeltron used. Once saturated, the detector was found to exhibit hysteresis between rising and falling input flux and output counts.

cond-mat.mtrl-sci↗

arXiv1994

On the Non-invasive Measurement of the Intrinsic Quantum Hall Effect

With a model calculation, we demonstrate that a non-invasive measurement of intrinsic quantum Hall effect defined by the local chemical potential in a ballistic quantum wire can be achieved with the aid of a pair of voltage leads which are separated by potential barriers from the wire. Büttiker's formula is used to determine the chemical potential being measured and is shown to reduce exactly to the local chemical potential in the limit of strong potential confinement in the voltage leads. Conditions for quantisation of Hall resistance and measuring local chemical potential are given.

cond-mat↗