Thermal Treatments and Photoluminescence Properties of ZnO and ZnO:Yb Films Grown by Magnetron Sputtering

Abstract

This work is on ZnO and ZnO:Yb (0.3 at%) films prepared on (100) Si substrates by magnetron sputtering and deals with their structural and photoluminescence evolutions upon annealing at different temperatures from 873 to 1173 K during 1 h under N 2 atmosphere. The microstructural characterizations reveal that, for both sample series, annealing treatment improves the crystallinity of ZnO of the upper part of the films. However, (002) textured ZnO columnar growth is only observed for ZnO films. For annealing temperatures higher than 973 K, rare earth and Si diffusions toward the film/substrate interface are observed resulting in the appearance of a zinc silicate phase for ZnO films and a composite material made of nanoscale ZnO grains surrounded by an amorphous phase for ZnO:Yb films. In addition, photoluminescence measurements show that Yb doping in ZnO results in a lower integrated photoluminescence intensity compared to that of ZnO films and the photoluminescence response in the visible spectral range is also modified most probably due to the presence of dopant. Furthermore, the PL intensity at 980 nm originating from electronic transitions between 2 F 5/2 and 2 F 7/2 levels of Yb 3þ ion increased with temperature. At last, the evolutions of the PL emissions with temperature from the ZnO defects are discussed.

Experimental Realization of 1400–2100 nm Broadband Emission for Wide-Bandwidth Optical Communication in Er–Tm Codoped ZnO Films and Devices

“…38,39 Thus, as for the detected Si 1TO mode in the ETZO films annealed at HTs (>900 °C), there might be two main reasons. First, the HT annealing process would promote the diffusion of Si from Si substrate to RE-doped ZnO films, just as reported by Guillaume et al 28 So the emergence of Si signals in the films annealed at 1000 and 1100 °C might come from Si in the ETZO films, which diffused from Si substrates. Second, the more obvious Si 1TO signal occurs in 1100 °C annealed film.…”

“…Finally, to optically activate both Er 3+ and Tm 3+ ions, the as-deposited films were annealed for 30 min at different temperatures in the range of 800–1100 °C under N 2 atmosphere. The crucial reason that the films were annealed under N 2 atmosphere was to avoid the oxidization of the Si substrate for the EL device. , The oxidized Si contacting with Al electrode that was not of benefit for the formation of Ohmic contact resulted in the performance degradation of the EL device. The average concentrations of Er and Tm in the ETZO film are about 0.2 and 0.6 at.…”

“…The crucial reason that the films were annealed under N 2 atmosphere was to avoid the oxidization of the Si substrate for the EL device. 28,29 The oxidized Si contacting with Al electrode that was not of benefit for the formation of Ohmic contact resulted in the performance degradation of the EL device. The average concentrations of Er and Tm in the ETZO film are about 0.2 and 0.6 at.…”

ZnO – Yb2O3 composite optical ceramics: Synthesis, structure and spectral-luminescent properties

“…Various ZnO materials doped with ytterbium ions were previously developed and studied, i.e., quantum dots [21], nanomaterials [22][23][24][25][26][27][28][29][30][31], films [33][34][35][36][37][38][39][40][41][42][43], microspheres [44] and ion implanted single crystals [45,46].…”

“…The authors of all these studies mentioned that an addition of ytterbium ions modifies the structure, texture and properties of ZnO materials. In a series of publications [24,25,[32][33][34]39,41,[43][44][45], the authors did not register any crystalline phase other than ZnO by the X-ray diffraction (XRD) analysis, which led them to conclusion that Yb 3+ ions enter into the ZnO lattice. Any amount of Yb in other phases was claimed to be below the detection limit of the XRD analysis [41].…”