Archana Venugopal

Low temperature synthesis of graphite on Ni films using inductively coupled plasma enhanced CVD

Controlled synthesis of graphite at low temperatures is a desirable process for a number of applications. Here, we present a study on the growth of thin graphite films on polycrystalline Ni films at low temperatures, about 380 °C, using inductively coupled plasma enhanced chemical vapor deposition. Raman analysis shows that the grown graphite films are of good quality as determined by a low ID/IG ratio, ∼0.43, for thicknesses ranging from a few layers of graphene to several nanometer thick graphitic films. The growth of graphite films was also studied as a function of time, precursor gas pressure, hydrogen concentration, substrate temperature and plasma power. We found that graphitic films can be synthesized on polycrystalline thin Ni films on SiO2/Si substrates after only 10 seconds at a substrate temperature as low as 200 °C. The amount of hydrogen radicals, adjusted by changing the hydrogen to methane gas ratio and pressure, was found to dramatically affect the quality of graphite films due to their dual role as a catalyst and an etchant. We also find that a plasma power of about 50 W is preferred in order to minimize plasma induced graphite degradation.

Sub-threshold current based acceleration and modeling of OFF-state TDDB in drain extended NMOS and PMOS transistors

It is not always practical to observe OFF-state drain-to-gate dielectric breakdown in power transistors due to the upper limit set to stress voltage by junction breakdown. In this paper we demonstrate that OFF-state breakdown in drain extended power transistors can be accelerated by increasing the channel current (IS) by biasing the transistor in sub-threshold. We also show that the charge pumping scaling factors along with observed breakdown times can be used to build an IS and VDG dependent model to extrapolate failure times at operating bias conditions.