Synthesis Characterization and Applications of Diamond and Graphene Based Materials

  • 屈 岳杰

Student thesis: Doctoral Thesis

Abstract

In the dissertation the studies are divided into three parts First to deposit a tungsten layer on nanodiamond pre-seeded silicon substrates to observe the effects on the deposition of ultrananocrystalline diamond (UNCD) films Tungsten carbide formed by reactions of the tungsten layer with carbon containing plasma species provides favorable (001) crystal planes for nucleation of (111) crystal planes by Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) in argon diluted methane plasma and further improves the total density of diamond seeds/nuclei UNCD films grown at different gas pressures on pre-seeded nanodiamond and heteroepitaxially grown diamond nuclei were characterized by Raman scattering FE-SEM and HR- transmission electron microscopy Bias-enhanced nucleation and growth (BEN-BEG) of carbon nano-pillars containing UNCD on silicon substrates by low-pressure MPECVD in a hydrogen-rich gas mixture with methane is reported Direct-current (DC) biasing of the substrate in a constant-current mode is applied to substrates which are pre-heated to 8000C and 9000C to result in a negative bias voltage of greater than 350 volts through-out the nucleation and growth process Sputtering of UNCD clusters and ion-assisted chemical vapor deposition by bias enhanced bombardment of energetic ions is attributed to the formation of carbon nano-pillars The porous UNCD with high-density nano-pillars exhibits improved electron field emission characteristics compared to smooth and solid UNCD films In addition a SERS application for biomedical molecules detection using nano-pillars diamond due to high effective surface areas Second nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) and multi-layer-graphene-like hybrid carbon films have been synthesized by microwave plasma enhanced chemical vapor deposition (MPECVD) on oxidized silicon which is pre-seeded with diamond nanoparticles MPECVD of N-UNCD on nanodiamond seeds produces a base layer from which carbon structures nucleate and grow perpendicularly to form standing carbon platelets High-resolution transmission electron microscopy and Raman scattering measurements reveal that these carbon platelets are comprised of ultrananocrystalline diamond embedded in multilayer-graphene-like carbon structures UNCD grains in the N-UNCD base layer and the hybrid carbon platelets serve as high-density diamond nuclei for the deposition of an electrically insulating UNCD film on it Biocompatible carbon-based heaters made of low-resistivity hybrid carbon heaters encapsulated by insulating UNCD for possible electrosurgical applications have been demonstrated In addition by using a novel nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) encapsulated NG/copper complex anodes N-UNCD enables robust solid electrolyte interphase (SEI) formed by NG/electrolyte chemical reactions and suppresses stress induced cracks of the SEI and NG particles and the subsequent loss of anode conductivity Third the monolayer graphene (Gr) dendrite was synthesized by thermal CVD The unique dendritic structure of the graphene has a high aspect ratio with primary and secondary branches that exhibits excellent EFE properties Electrical characteristics for a single main branch were investigated from graphene back-gate FETs The highest hole carrier mobility is up to 9200 cm2/Vs after 2500C thermal treatment in vacuum The photoresponse of Gr dendrites applied above 1mV bias exhibits negative photoconductivity Hot carriers scattering effect influence carriers transport under light illumination It reduces photocurrent due to hot carriers scattering The strong effects of positive and negative photovoltaic are appeared at a bias condition of 1mV It is related to band bending with doping effect among graphene-electrode contacts
Date of Award2014 Aug 14
LanguageEnglish
SupervisorYon-Hua Tzeng (Supervisor)

Cite this

Synthesis Characterization and Applications of Diamond and Graphene Based Materials
岳杰, 屈. (Author). 2014 Aug 14

Student thesis: Doctoral Thesis