Identification of Sublattice Damages in Swift Heavy Ion Irradiated N-Doped 6H-SiC Polytype Studied by Solid State NMR

Abstract

We have studied N-doped 6H-SiC in its pristine and Swift Heavy Ion (SHI) irradiated (150 MeV Ag(12+) ions) forms by solid state Nuclear Magnetic Resonance (NMR) at 7.01 T using (13)C and (29)Si as probe nuclei under magic angle spinning. We show that increased levels of nitrogen doping, than used before, lead to the observation of Knight shifts emanating from an increase in electron density in the conduction band, which in (13)C far exceed those in (29)Si MAS spectra. We have rationalized the differential effects in the MAS spectra and site-dependent paramagnetic shifts in terms of the nitrogen doping at the A, B, and C lattice sites. N-doping has a profound effect on (29)Si spin-lattice relaxation, and the site-dependent relaxation behavior is attributed to a difference in conduction electron properties at the different lattice sites. (29)Si T(1) measurements serve to identify the sublattice damages in SHI irradiated 6H-SiC. By determining the spin-lattice relaxation rates as a function of the SHI irradiation ion fluences, the change in relaxation behavior is correlated to the damage production mechanism. The sublattice damage leads to discernable changes in the interaction between the mobile unpaired electrons in the conduction band and the nuclear site, which profoundly influence the NMR relaxation properties. Our relaxation studies also provide evidence for site-dependent localized effects and a decrease in carrier spin density in the conduction band for the SHI irradiated 6H-SiC.

Effect of Surface Topology on the Apparent Thermal Diffusivity of Thin Samples at LFA Measurements

“…An accurate measurement of the surface temperature of a turbine blade and the control of its temperature distribution is an important basis for diagnosing turbine blade failure. The methods of measuring the surface temperature of turbine blades mainly include thin-film thermocouples [ 21 , 22 , 23 ], temperature indicating paint [ 24 ], infrared radiation [ 25 , 26 , 27 ], and irradiation crystals [ 28 , 29 , 30 ]. Based on the advantages of irradiating crystals, the authors [ 20 ] proposed an easy and cheap method of temperature measurement using a thin-film crystal.…”

Fabrication of Weak C-Axis Preferred AlN Thin Film for Temperature Measurement

“…Accurately measuring the surface temperature of the turbine blade and mastering its temperature distribution is an important basis for diagnosing turbine blade breakdown. Surface temperature measurement methods of turbine blades mainly include thin-film thermocouple [ 1 , 2 , 3 ], temperature-indicating paint [ 4 ], infrared radiation [ 5 , 6 , 7 ], and irradiation crystals [ 8 , 9 , 10 ]. Thin-film thermocouple technology has the advantages of high integration, but it is not applicable for high-speed rotating blades.…”