Electron spin resonance of ultraviolet radiation induced defects in ZnO thermal control coating pigment

Abstract

Electron spin resonance measurements on differently treated zinc oxide powder reveal that the resonance signal at g = 1.956 is due to one electron trapped oxygen ion vacancy level, at a depth of (0.31 ± 0.02) eV below the conduction band. The electrons at this level are delocalized. Schottky barrier influences nearly the entire bulk of the powder sample and the bending of the bands caused by chemisorbed oxygen puts the vacancy level above the Fermi level almost through the entire bulk.

Fundamentals of zinc oxide as a semiconductor

“…Note that Sancier in 1970 also favored assigning the g ∼ 1.96 line to electrons in the conduction band [174], and Neumann in 1981 observed that doping with Al, Ga or In increases the intensity of the g ∼ 1.96 signal. The g ∼ 1.96 signal has also been reported to be enhanced under UV illumination [169,[171][172][173][174][175][176]178]. UV light can indeed promote electrons into the conduction-band states in ZnO, consistent with the g ∼ 1.96 line corresponding to electrons in delocalized states.…”

“…Most of the experimental investigations of oxygen vacancies in ZnO to date have relied on electron paramagnetic resonance (EPR) measurements [38,40,47,[166][167][168][169][170][171][172][173][174][175][176][177][178][179][180][181][182][183]188]. Many of these studies fall into two categories, depending on the value of the g-factor: one set of reports associates oxygen vacancies with a g value of ∼1.96 [38,40,[169][170][171][172][173][174][175][176][177][178][179][180][181], the other with g ∼ 1.99 [47, 166-168, 182, 183, 188] (a table containing an overview of these results was included in [27]). There is, however, overwhelming evidence that oxygen vacancies are actually associated with the g ∼ 1.99 line.…”

Enhancement and tailoring of photoluminescence by the use of metallic nanostructures

“…Note that Sancier in 1970 also favoured assigning the g∼1.96 line to electrons in the conduction band [166] observed that doping with Al, Ga or In increases the intensity of the g∼1.96 signal. The g∼1.96 signal has also been reported to be enhanced under UV illumination [155,[164][165][166]168,173]. UV light can indeed promote electrons into the conduction-band states in ZnO, consistent with the Vlasenko and Watkins have also carried out ODEPR measurements in high-quality ZnO single crystals [170], whose results are in good agreement with the first-principles results…”

“…Therefore, it is possible to detect EPR signals due to V O + upon photoexcitation at quite low temperatures, but if the excitation is removed and the temperature is raised, these signals decay. Most of the experimental investigations of oxygen vacancies in ZnO have relied on electron paramagnetic resonance (EPR) measurements [146,[155][156][157][158][159][160][161][162][163][164][165][166][167][168][169]. Many of these studies fall into two categories, depending on the value of the g-factor: one set of reports associates oxygen vacancies with a g value of ∼1.96 [120,124,[155][156][157][158][163][164][165][166][167][168][169], the other with g∼1.99 [159,160,162,[170][171][172].…”

“…Most of the experimental investigations of oxygen vacancies in ZnO have relied on electron paramagnetic resonance (EPR) measurements [146,[155][156][157][158][159][160][161][162][163][164][165][166][167][168][169]. Many of these studies fall into two categories, depending on the value of the g-factor: one set of reports associates oxygen vacancies with a g value of ∼1.96 [120,124,[155][156][157][158][163][164][165][166][167][168][169], the other with g∼1.99 [159,160,162,[170][171][172]. There is, however, evidence that oxygen vacancies are associated with the g∼1.99 line.…”