Thermal Conductivity Degradation and Microstructural Damage Characterization in Low-Dose Ion Beam-Irradiated 3C-SiC VINAY S. CHAUHAN, M. FAISAL RIYAD, XINPENG DU, CHANGDONG WEI, BEATA TYBURSKA-PU ¨ SCHEL, JI-CHENG ZHAO, and MARAT KHAFIZOV This study assesses the impact of low-dose and low-temperature irradiation on the properties of cubic silicon carbide (3C-SiC). 3C-SiC was irradiated with Kr ions to different fluences at 420 K (147 °C). Raman spectroscopy was used to investigate the impact of irradiation-induced defects on vibrational modes and time-domain thermoreflectance (TDTR) was used to measure thermal conductivity. We observe a noticeable reduction in thermal conductivity with increasing fluence. Analysis of Raman spectra reveals the longitudinal optical (LO) and transverse optical (TO) modes with noticeable peak broadening of LO mode with increasing dosage. We also notice a decrease of ratio of peak intensities of LO and TO modes in irradiated samples. We observe a correlation between the thermal conductivity reduction and the decrease in the peak intensity ratio and attribute this to the accumulation of charged vacancy defects. DOI: 10.1007/s40553-017-0107-3 Ó ASM International (ASM) and The Minerals, Metals & Materials Society (TMS) 2017 I. INTRODUCTION SILICON carbide (SiC) is a wide-band gap semicon- ductor and a hard ceramic; it has attracted lot of research attention in the past because of its stable chem- ical, mechanical, and physical properties in extreme environments. [1] SiC is actively investigated as a struc- tural material in both fission and fusion nuclear reactors and as a potential material for fuel cladding in light- water fission reactors. [2–5] SiC is also considered as a plasma chamber material for fusion reactors. [6] TRIstructural-ISOtropic fuel relies on the mechanical integrity provided by a combination of pyrolytic carbon and SiC layers to achieve exceptional fission product retention. [7–9] In these applications, SiC is exposed to extreme environments such as high temperature, water, steam, and corrosive molten salts, and bombarded with heavy ions and energetic neutrons. These environmental conditions are detrimental to its mechanical, chemical, and structural stability. [6] While most applications require structural integrity, some require SiC’s ability to transport heat efficiently. As a result, thermal conductivity has been widely investigated as one of the critical properties of SiC. [1,10–14] Thermal conductivity reduction can lead to poor thermal management within the reactor, which is especially important for applica- tions such as nuclear fuel cladding for light-water reactors and breeding blanket in fusion reactors. [6,15–18] SiC is also an important material in the semiconduc- tor industry because of its large electronic band gap, high electron mobility, and high breakdown volt- age. [19,20] Dopants used for SiC diffuse poorly in the material, which makes ion implantation an alternative method for doping. [21] Displacement damage caused by the implantation may lead to undesired changes and deteriorated performance of the device. On the other hand, SiC-based sensors are used in radiation environ- ments, where the ionization effects play an important role. [22] Raman spectroscopy was extensively used to study the defects in SiC which are mainly associated with the dopants that are introduced to tailor its electronic properties and to a lesser extent on the ion-irradiated samples of SiC. [23–27] Raman peaks depend on the crystalline structure and electronic polarizabilities of the Si-C bonds which can be significantly impacted by the defects. The sensitivity of Raman spectra to defects has been utilized as a tool to study crystalline structure and disorder and to characterize dopants and irradiation-in- duced displacement damage. [28–30] Majority of the previous studies on radiation dam- age-induced thermal conductivity degradation have been based on the application of laser flash approach VINAY S. CHAUHAN, M. FAISAL RIYAD, and MARAT KHAFIZOV are with the Department of Mechanical and Aerospace Engineering, The Ohio State University, 201 W. 19th Ave., Columbus, OH 43210. Conatct e-mail: khafizov.1@osu.edu XINPENG DU, CHANGDONG WEI, and JI-CHENG ZHAO are with the Depart- ment of Materials Science and Engineering, The Ohio State University, 2041 College Road, Columbus, OH 43210. BEATA TYBURSKA- PU ¨ SCHEL is with the Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Dr., Madison, WI 53706. Manuscript submitted June 30, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS E