Effect of vacuum annealing on evaporated pentacene thin films for memory device applications

• Memory device performance in pentacene improved considerably with annealing.
• ON/OFF ratio of the pentacene device increases due to annealing.
• Threshold voltage reduces from 2.55 V to 1.35 V due to annealing.
• Structure of pentacene thin films is also dependent on annealing temperature.

Thin films of pentacene were deposited thermally onto glass substrates and annealed at 323 K, 373 K, 423 K, 473 K and 523 K in high vacuum. Effect of annealing on the morphological and structural properties of these films was studied. X-ray diffraction patterns confirmed the crystalline nature of the films. Electrical studies for the use as write once read many (WORM) memory devices were done for the vacuum deposited pentacene thin films on indium tin oxide coated glass. Due to annealing, a sharp increase in the ON/OFF ratio of current and a decrease in threshold voltage were observed at around 373 K. This device showed a stable switching with an ON/OFF current ratio as high as 109 and a switching threshold voltage of 1.35 V. The performance of the device degraded above 423 K due to the changes in the crystallinity of the film.

Switching of ITO/pentacene/Al thin films for different annealing temperatures.Figure optionsDownload as PowerPoint slide