Delivered by Ingenta to: Nanyang Technological University IP: 188.72.127.151 On: Mon, 06 Jun 2016 19:01:34 Copyright: American Scientific Publishers RESEARCH ARTICLE Copyright © 2011 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 11, 8185–8189, 2011 Diamond Layers Grown by Chemical Vapor Deposition on NbN Systems and NbN/SiO 2 -Based Devices S. Orlanducci 1 ∗ , V. Guglielmotti 1 , I. Cianchetta 1 , M. Lucci 2 , F. Toschi 1 , E. Tamburri 1 , and M. L. Terranova 1 1 Dip. di Scienze e Tecnologie Chimiche and Minima Lab, University of Rome “Tor Vergata”, Via della Ricerca Scientifica 1-00133 Rome, Italy 2 Dip. di Fisica and MINAS Lab, University of Rome “Tor Vergata”, Via della Ricerca Scientifica 1-00133 Rome, Italy Deposits of individual diamond grains and continuous polycrystalline diamond layers have been gen- erated by means of a HFCVD technique onto different types of untreated or seeded NbN surfaces. To test the feasibility of using diamond layers as protective coatings for aerospace applications, we carried out diamond deposition onto the lithographically defined NbN microelectrodes of a NbN/SiO 2 multifinger device. The morphological and structural features of the diamond deposits and of the substrates were characterized by FE-SEM, XRD and Raman spectroscopy. The preferential growth of diamond on the superconductive NbN enables the selective coating of the NbN microstripes sputtered on the insulating SiO 2 . Moreover the diamond coating procedure is able to preserve the structural integrity of the substrate material and to retain the shaped architecture of the device. For the polycrystalline diamond layers grown on NbN a residual stress of −9.8 GPa, largely due to thermal stress, has been estimated by Raman analysis. The diamond coatings of the NbN-based architectures result to be mechanically stable. Keywords: CVD Diamond, NbN, Patterned Substrate. 1. INTRODUCTION In recent years the technology of low-pressure/low- temperature CVD synthesis of diamond layers, proposed in the 80s and now well settled, has been extended to aerospace applications. 1 The use of diamond as coating material in the spa- tial technology is indeed extremely attractive for the mechanical and thermal properties of the diamond phase (strength, toughness, radiation resistance, hardness). 2 The proposed application are for re-entry parts of space vehi- cles, rocket nozzle and propellers for small spacecraft (ion thrusters). 3–5 Additional applications include the radiation shielding of electronic components and the heat dissipation in high-powered electronic devices. 6 7 On the other hand niobium nitride (NbN), due to its stability and to the superconducting behaviour at relatively high temperature, is a material with a vast potential for applications in innovative superconducting devices such as single photon detector and bolometer. 8 9 In some aerospace applications, however, the NbN surfaces have been shown to suffer radiation impact damage and oxidation. 10 ∗ Author to whom correspondence should be addressed. The present study was motivated by the technological requirement to set a methodology for deposition of dia- mond layers on NbN-based systems and for the engineered coating of NbN/SiO 2 -based devices. 2. EXPERIMENTAL DETAILS The setting of the experimental conditions for the growth of diamond films on NbN was achieved using as substrates Si/SiO 2 wafers partially covered by 400 nm thick NbN layers. The deposition of the NbN layers was realized by means of DC-RF magnetron sputtering. In order to compare the diamond growth process on NbN with respect to the well-known one on SiO 2 , we have produced patterned substrates by masking a selected area of the SiO 2 substrate during the NbN sputtering process. The diamond depositions were performed in a Hot Fil- ament Chemical Vapor Deposition (HF-CVD) apparatus using CH 4 /H 2 mixtures activated by a Ta filament heated at 2100 ± 10  C, and positioned at 10 mm from the substrates. 11 The experimental optimized parameters are listed below: • substrate temperature: 700  C ± 10  C; • H 2 flow: 198 sccm; J. Nanosci. Nanotechnol. 2011, Vol. 11, No. 9 1533-4880/2011/11/8185/005 doi:10.1166/jnn.2011.5095 8185