Switching in V2O5GeO2PbO glasses

Journal of Non-Crystalline Solids, 13 (1973/74) 355 - 356. © North-Holland Publishing Company

LETTERS TO THE EDITOR S W I T C H I N G IN V 2 O s - G e O 2 - P b O

GLASSES

H. GAHLMANN and R. BRt)CKNER lnstitut fftr Nichtmetallische Werkstoffe -Anorganische Werkstoffe, Technische Universiti~t Berlin, Germany Received 30 August 1973 Since the discovery by Ovshinsky [ 1] of switching in amorphous materials an ever increasing number of investigations on the switching behaviour has been published. The main interest was concentrated on chalcogenide glasses, less on oxide glasses which appeared to be less promising with respect to their switching characteristics. It is still a matter of controversy as to whether a partial crystallization observed in chalcogenide glasses, e.g. by DTA analysis, or other possibly existing mechanisms can give a satisfactory explanation for the various switching effects. However, switching has also been observed in oxide glasses. Drake et al. [2] found a switching effect in copper containing phosphate glasses and gave a structural interpretation which did not assume the presence of crystals. R. Holzinger and O. Holzinger [3] observed a negative resistance in phosphate and borate glasses. It also appears that glasses containing V205 in combination with suitable components provide promising systems in which to observe switching [4]. The basis of our own investigations are glasses from the ternary system V 2 0 5 - G e O 2 - P b O . This system offfers a wide glass-forming region. X-ray investigations show no crystallization peaks after melting and cooling to room temperature. D.C. measurements with a series resistance of 100 k~2 reveal switching in this ternary system, and even in the binary systems V 2 0 5 - G e O 2 and V 2 0 5 - P b O , especially threshold behaviour in the former and memory behaviour in the latter. As examples, the behaviours of glasses of both binary systems are illustrated in figs. 1 ans 2, each composition is 50 : 50 wt %. In the case of threshold switching a forming or first-fire voltage, which is about ten times the magnitude of the threshold voltage, has to be applied to the glass prior to switching. It should be mentioned that also the on-state (high conductive state) shows a negative resistance. It is remarkable that the on-state of the memory glass shows a reversible characteristic deviation from ohmic behaviour at low 1- V values. In order to switch this glass from the high to the low conductive state a short high current pulse has to be applied. These preliminary results stimulate the further study of the switching characteristics of the total ternary system in more detail; d.c. and pulse measurements are now in progress.

356

1t. Gahlmann, R. Bruckner, Switching in V20 s -GeO 2 -PbO Glasses

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Fig. 1. Threshold switching in a V20 s -GeO2 glass. Electrode distance d ~ 40/zm, UTh: threshold voltage, UH: holding voltage.

100 200 300 400 --U[V] Fig. 2. Memory switching in a V 2 as -PbO glass. Electrode distance d ~ 30/zm.

References [1] S.R. Ovshinsky, Phys. Rev. Lett. 21 (1968) 1450. [2] C.F. Drake et al., Phys. Slat. Sol. 32 (1969) 193; IEEE Trans. Electron Devices, ED-20 (1973) 144. [3] R. Holzinger and O. Holzinger, Z. Angew. Phys. 28 (1970) 196. [4] V.I. Gaman, Izv. VUZ Fiz 2 (1972) 57; 3 (1972)45.