Variability Effects in Carbon Electronic Materials

Guangyu Xu
Advisor: Kang L. Wang

Tuesday, October 12, 2010 at 12:00pm
Engr IV Faraday Room 67-124

Abstract:
Variability effects are especially critical when the device size scales down into sub-micron dimensions, which has been limiting the state-of-art Si CMOS production processes. Recent advances of low-dimensional nanoscale materials offer solutions in profound applications and raise much focus. However, as the size scales down, quantum effects start to appear and increasingly impact the device performance. Inherent to nanoscale electronic material systems, large conductance fluctuations due to the surface traps have become a critical issue to be addressed for scalable electronics.

In this work, we systematically characterized the variability effect of carbon electronic materials including carbon nanotube, graphene and graphene nanoribbon, which are of main scientific and practical concern for their extraordinary properties. In terms of measuring low-frequency conductance fluctuations, or low-frequency noise, we obtained the following results: 1) Lower noise could be obtained in carbon nanotube through surface passivation by 40% noise reduction. 2) Charged-impurity induced spatial charge inhomogeneity could strongly affect the noise behavior in graphene, which features an abnormal gate-dependence of noise behavior: M-shape in single-layer graphene and V-shape in bi-layer graphene. 3) Enhanced conductance fluctuation is observed in graphene nanoribbon, where the gate-dependence noise exhibits peaks whose position quantitatively match the quasi-one-dimensional subband structure.

Biography:
Guangyu Xu received B.S. in Fundamental Science (Mathematics and Physics) and M.S. in Electrical Engineering from Tsinghua University, China in 2003 and 2006, respectively. From 2006, he joined the DRL group of UCLA for his Ph. D. research.