ZnO as dielectric for optically transparent non-volatile memory

This paper discusses the application of a DC sputtered ZnO thin film as a dielectric in an optically transparent non-volatile memory. The main motivation for using ZnO as a dielectric is due to its optical transparency and mechanical flexibility. We have established the relationship between the electrical resistivity (p) and the activation energy (E-a) of the electron transport in the conduction band of the ZnO film. The p of 2 x 10(4) 5 x 10(7) Omega-cm corresponds to E-a of 0.36-0.76 eV, respectively. The k-value and optical band-gap for films sputtered with Ar:O-2 ratio of 4:1 are 53 +/- 3.6 and 3.23 eV, respectively. In this paper, the basic charge storage element for a non-volatile memory is a triple layer dielectric structure in which a 50 nm thick ZnO film is sandwiched between two layers of methyl silsesquioxane sol-gel dielectric of varying thickness. A pronounced clockwise capacitance-voltage (C-V) hysteresis was observed with a memory window of 6 V. The integration with a solution-processable pentacene, 13,6-N-Sulfinylacetamodipentacene resulted in an optically transparent organic field effect transistor non-volatile memory (OFET-NVM). We have demonstrated that this OFET-NVM can be electrically programmed and erased at low voltage (+/- 10 V) with a threshold voltage shift of 4.0 V. (C) 2009 Elsevier B.V. All rights reserved.