Metal/a-Si:H/metal thin film structures have been widely used in various applications as reversible and irreversible memory switching devices. Theses memory switching devices can change their resistance in discrete jumps or continuously depending upon the applied voltage. During the electroforming, some parts of the top metal material diffuse into the a-Si:H matrix, resulting in the creation of a highly conducting filament which decreases device resistance from a high value of 1 to 100 M$＼ohm$ irreversibly, to approximately 1 K$＼ohm$ or below.
In this experiment, we fabricated metal/p-a-Si:H/metal structure switching devices with 4 different top metals (Cr, Ni, Al and Ag) using photo-CVD. The boron doped p-a-Si:H, with a layer thickness 0.2 ㎛, was prepared by UV decomposition of silane $(SiH_4)$ containing typically $1.2 x 10^4$ ppm by volume of diborane $(B_2H_6)$. Instead of applying the voltage pulse for electroforming and switching, we swept the voltage to investigate the switching properties of devices. The experiments showed that devices have low electroforming & switching voltage (~ 10 V or less, < 5 V) and very high resistance ratio $(~ 10^6)$ compared with conventional devices.