INSTITUTE OF PHYSICS PUBLISHING NANOTECHNOLOGY Nanotechnology 12 (2001) 258–264 PII: S0957-4484(01)18474-6 The effect of an electric field on the chemical vapour deposition of (100) diamond Jeung Ku Kang 1 and Charles B Musgrave 1,2 1 Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305-2205, USA 2 Department of Chemical Engineering, Stanford University, Stanford, CA 94305-5025, USA Received 31 October 2000, in final form 6 March 2001 Published 24 August 2001 Online at stacks.iop.org/Nano/12/258 Abstract The scanning tunnelling microscope (STM) has been used to modify surfaces with atomic resolution and has consequently been proposed as a tool for nanotechnology. Here we examine a process for deposition of (100) diamond under a localized electric field. We use ab initio quantum-chemistry techniques to investigate the effect of an electric field on the chemical vapour deposition of (100) diamond. The field approximates the field of an STM by using a point charge placed 15 Å above the surface to create a 0.64 V Å -1 field at the dimer. Our study explores the effect of this electric field on CH 3 adsorption, and the dimer-opening and ring-closing steps of the Brenner–Garrison diamond CVD mechanism. CH 3 adsorption is exothermic by 84 kcal mol -1 and is not affected by the electric field. The dimer-opening and ring-closing steps are sensitive to the applied field: the dimer-opening barrier is reduced from 9.6 to 6.0 kcal mol -1 , while the barrier of the ring-closing step is reduced from 13.6 to 11.0 kcal mol -1 . Our results indicate that the rate of CVD diamond growth can be enhanced by the application of an electric field, in agreement with experiment. 1. Introduction Eigler and Schweizer first used a scanning tunnelling microscope (STM) to position individual atoms on a single- crystal surface with atomic precision [1]. Musgrave et al [2] later proposed a nanofabrication tool to abstract hydrogen from a hydrogen-passivated surface using an ethynyl radical attached to a scanning probe microscope (SPM) tip. The idea was originally to use a radical that would form a strong enough bond to the surface hydrogen that the abstraction barrier would be small. The disadvantage of this tip is in that it must be regenerated after each use. However, it is well demonstrated that the field or current of the STM can be used to modify a surface with atomic or nanoscale precision [3, 4]. This approach appears to be more practical given the current state of scanning probe technology because it does not require the attachment or regeneration of radicals. Nanotechnology processes that use the electric field of an STM tip to control surface chemical reactions by either modifying activation barriers or selecting between alternative reaction pathways will allow us to construct a wide range of nanoscale devices. For example, the modification of the barriers for the elementary reaction steps of diamond growth would demonstrate that the deposition and modification of diamond surfaces can be controlled with an electric field to create atomically precise components. The growth of diamond films has been of great interest because diamond has a wide range of electronic, mechanical and optical properties. One reason for the wide range of properties is the ability of carbon to adopt sp, sp 2 or sp 3 hybridization in materials. Metal semiconductor field- effect transistors (MESFETs) [5] fabricated on hydrogen- terminated diamond films capable of high speed and with good temperature stability have been demonstrated recently. This, as well as other applications in integrated circuit technology, has motivated efforts to grow diamond films of high quality in the microelectronics industry. Microwave-enhanced plasma CVD (MEPCVD) at a high ratio of CH 4 /H 2 is used for the growth of smooth diamond films. In addition to high speed and temperature stability, MESFETs fabricated on these films have 0957-4484/01/030258+07$30.00 © 2001 IOP Publishing Ltd Printed in the UK 258