SSO Seminar
Wednesday, October 3, 2012 - 16:00 to 17:00
Weniger 304
Event Speaker: 
Prof. John Conley, OSU EECS
Local Contact: 

In this talk, two topics will be discussed:

1) Resistive random access memories (RRAM), also known as memristors, have emerged as a possible next-generation replacement for non-volatile flash memory due to their simple structure and potential for rapid program/erase speed, high areal density, and low power consumption. Thin film transistors (TFT) based on the transparent wide bandgap amorphous oxide semiconductor indium-gallium-zinc-oxide (IGZO) are approaching commercialization as a replacement for amorphous Si in high performance large area macroelectronic applications such as liquid crystal displays (LCDs). Zinc-tin-oxide (ZTO) is considered to be the leading alternative material to IGZO for TFT applications. While both IGZO and ZTO have good electron mobility, exhibit good TFT performance, have high transparency, and can be processed at low temperatures, ZTO has the advantage that it does not require In or Ga, two increasingly expensive elements. Bipolar resistive switching is demonstrated in solution deposited amorphous ZTO. Overall, ZTO shows promise as a low cost material for embedding transparent low power memory with logic on TFT displays with little change in process flow.

2) Metal-insulator-metal (MIM) based tunneling devices have been proposed for macroelectronic applications such as backplanes for liquid-crystal displays (LCDs), as well as for high speed applications such as hot electron transistors, infrared (IR) detectors, and optical rectennas for IR energy harvesting. The desired current density versus electric field (J-ξ) behavior for the majority of these applications is high nonlinearity and asymmetry at low voltage. Although asymmetry can be achieved using asymmetric metal electrodes, the amount of asymmetry achievable is limited by the workfunction difference that can be obtained using practical metal electrodes. Another way to introduce low voltage asymmetry and nonlinearity is through the use of a MIIM structure in which dielectrics with different bandgaps and band-offsets are combined to produce an asymmetric tunnel barrier. In this work, amorphous metal ZrCuAlNi bottom electrodes, atomic layer deposition (ALD), and Al top electrodes are combined to investigate the impact of bilayer dielectric tunnel barriers (HfO2/Al2O3, ZrO2/Al2O3, and HfO2/ZrO2) on MIIM tunnel diode operation. It is found that bilayer tunnel barriers allow tuning of MIIM operation independent of and in addition to electrode asymmetry and that I-V asymmetry is a sensitive function of the thickness of the individual dielectric layers as well as the arrangement of the individual layers with respect to the asymmetric work function metal electrodes. MIIM diodes have been fabricated that exhibit improved asymmetry over standard asymmetric electrode MIM diodes. These results representing an advancement in the understanding necessary to engineer thin film MIM tunnel devices for microelectronics applications.