Al-27 MAS NMR investigations on Al23Te77 glass: Observation of 5-coordinated Al and its influence on electrical switching

Al-27 Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopic studies show that Al resides in 4-, 5- and 6- fold coordination in bulk Al23Te77 glass. Also Al23Te77, glass is found to exhibit threshold type switching. Earlier studies report memory type switching in Al-Te glasses wherein Al has been found only in Al-4] and Al-6] environments. X-Ray Photo Electron Spectroscopic (XPS) measurements show the presence of Al2O3 in Al23Te77 glass network. The structural network of Al-Te glass has been cross linked by the presence of higher coordinated Al atoms. The structural reorganization becomes difficult due to the increased network connectivity. Thus, the memory switching (which requires an easy structural reorganization) is retarded, resulting in the observation of threshold switching