Delivered by Ingenta to: Acquisitions/Serials, Queen's University, IP: 178.57.68.153 On: Sun, 05 Jun 2016 19:45:17 Copyright: American Scientific Publishers ARTICLE Copyright © 2013 by American Scientific Publishers All rights reserved. Printed in the United States of America Energy and Environment Focus Vol. 2, pp. 85–89, 2013 (www.aspbs.com/efocus) Nanoindentation Studies of Metal Organic Vapor Phase Epitaxy Grown Ge/Si Heterostructures P. Joice Sophia 1 , D. Arivuoli 1, * , G. Attolini 2 , M. Bosi 2 , E. Buffagni 2 , C. Ferrari 2 , and F. Rossi 2 1 Crystal Growth Centre, Anna University, Chennai 600025, India 2 Istituto dei Materiali per l’Elettronica ed il Magnetismo, IMEM-CNR, Parco Area delle Sciencze, 37 A, 43124 Parma, Italy ABSTRACT The Ge/Si epilayers were grown by metal organic vapor phase epitaxy (MOVPE) technique at different growth temperatures. The hardness (H) and the reduced modulus (E r  were found to be 6.4–6.8 GPa and 109.9–119.9 GPa respectively using Berkovich indenter whereas Vickers indentation shows 10.1–11.0 GPa and 117.0–134.7 GPa respectively for the samples grown at different temperatures. The structural quality of the Ge/Si epilayers was investigated by high resolution X-ray diffraction (HRXRD). The full width at half maxi- mum (FWHM) of Ge/Si epilayers were measured for all the samples with respect to growth temperature. The broadening of the diffraction profile indicates the presence of inhomogeneous strain between the substrate and epilayers. From the atomic force microscopy (AFM) studies, presence of small grains on the surface was evidenced. KEYWORDS: Ge, Si, MOVPE, AFM, HRXRD, Nanoindentation. 1. INTRODUCTION In recent years, due to the increasing interest in nano- technology, deformation behavior of materials at nanoscale gains much attention in the fields of micro- and nano- electromechanical systems (MEMS, NEMS). The future challenge for information technology is to achieve innovative device structures using novel materials. Germa- nium (Ge) is recommended for transport channel device fabrication purposes because of its higher carrier injection velocity and mobility than silicon (Si). 1 Hence, a detailed investigation and improvement of Ge based epitaxy will be of much significance for future device fabrication. Ge/Si system is interesting and technologically important due to its applications in the field of photovoltaics, thermopho- tovoltaics, optoelectronics, computing, photodetectors for telecommunications, high-speed transistors, wireless and broadband communication. 1–3 Ge is easily adaptable with most of the prevailing Si fabrication techniques compared to the other III–V and II–VI semiconducting materials. 4 The response of Ge/Si to the depth sensing indenta- tion analysis has gained much attention in the past decade but there are very few reports available on nanoindenta- tion studies of Ge/Si. 8 10–13 The strain relaxation induced ∗ Author to whom correspondence should be addressed. Email: arivuoli@annauniv.edu Received: 5 November 2012 Accepted: 5 December 2012 defects like threading dislocations and misfit dislocations are seen in Ge/Si thin films because of the large lattice mismatch (∼ 4.2%) between Ge and Si atoms. 18 Oliver et al. 8 studied the thickness dependent phase transfor- mations of germanium thin films of different thicknesses ranging from 50–600 nm grown on Si (100) substrate. The poor quality of the Ge thin film deposited probably degrades the performance of thin films and also an obsta- cle for future improvements. In the present investigation, Ge/Si samples were grown by MOVPE technique at dif- ferent growth temperatures. The surface morphology and roughness were studied using AFM. The HRXRD stud- ies have been carried out to study the structural proper- ties. The nanoindentation technique was used to investigate the defects induced phenomenon on the Ge over Si het- erostructures using Berkovich and Vickers indenters. 2. MATERIALS AND METHODS A home-made horizontal MOVPE reactor without sub- strate rotation was used to deposit Ge films over n-type doped silicon (100) substrates. All the growths were car- ried out at a pressure of 60 mbar with hydrogen as car- rier gas and isobutylgermane (iBuGe) was used as Ge source. iBuGe was directly injected into the growth cham- ber with a partial pressure of 1941 × 10 -5 bar. Ge was heteroepitaxially grown on Si at different temperatures of 550  C, 600  C and 650  C and represented by symbols Energy Environ. Focus 2013, Vol. 2, No. 1 2326-3040/2013/2/085/005 doi:10.1166/eef.2013.1031 85