Characterization of Starburst Dendrimers by Electron Paramagnetic Resonance. 2. Positively Charged Nitroxide Radicals of Variable Chain Length Used as Spin Probes

1995 ◽  
Vol 117 (15) ◽  
pp. 4387-4398 ◽  
Author(s):  
M. Francesca Ottaviani ◽  
Eleonora Cossu ◽  
Nicholas J. Turro ◽  
Donald A. Tomalia
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Chain Length ◽  
Spin Probes ◽  
Nitroxide Radicals ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic ◽  
Positively Charged

Electron Paramagnetic Resonance Study of Carbon Antisite-Vacancy Pair in p-Type 4H-SiC

2007 ◽  
Vol 556-557 ◽  
pp. 453-456 ◽  
Author(s):  
T. Umeda ◽  
Norio Morishita ◽  
Takeshi Ohshima ◽  
Hisayoshi Itoh ◽  
Junichi Isoya
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Irradiation ◽  
Electron Paramagnetic Resonance Study ◽  
Dangling Bond ◽  
Charged State ◽  
Paramagnetic Resonance ◽  
Vacancy Pair ◽  
P Type ◽  
Electron Paramagnetic ◽  
Positively Charged

Carbon antisite-vacancy pair (CSiVC) is a fundamental defect in SiC, and is theoretically predicted to be very stable in p-type materials. However, this pair was found only in the form of a negatively charged state (i.e., the SI5 center = CSiVC −) in n-type and semi-insulating 4H-SiC, and yet, its presence has not been shown in p-type SiC. In this report, we present the first EPR observation on positively charged CSiVC pairs in p-type 4H-SiC. By carefully examining p-type samples after electron irradiation, we found a pair of new defects with C3v and C1h symmetries. They correspond to “c-axial” pairs (C3v) and “basal” pairs (C1h) of CSiVC +, respectively. The positively charged pairs are characterized by a strong 13C hyperfine interaction due to a dangling bond on a carbon antisite (CSi), which is successfully resolved for the c-axial pairs.

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