Publications

This paper investigates the effects of high dose rate ionizing radiation and total ionizing dose (TID) on tantalum oxide (TaO_x) memristors. Transient data were obtained during the pulsed exposures for dose rates ranging from approximately 5.0 ×10⁷ rad(Si)/s to 4.7 ×10⁸ rad(Si)/s and for pulse widths ranging from 50 ns to 50 μs. The cumulative dose in these tests did not appear to impact the observed dose rate response. Static dose rate upset tests were also performed at a dose rate of ~3.0 ×10⁸ rad(Si)/s. This is the first dose rate study on any type of memristive memory technology. In addition to assessing the tolerance of TaO_x memristors to high dose rate ionizing radiation, we also evaluated their susceptibility to TID. The data indicate that it is possible for the devices to switch from a high resistance off-state to a low resistance on-state in both dose rate and TID environments. The observed radiation-induced switching is dependent on the irradiation conditions and bias configuration. Furthermore, the dose rate or ionizing dose level at which a device switches resistance states varies from device to device; the enhanced susceptibility observed in some devices is still under investigation. As a result, numerical simulations are used to qualitatively capture the observed transient radiation response and provide insight into the physics of the induced current/voltages.

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This report discusses aspects of neuromorphic computing and how it is used to model microsystems.

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This paper evaluates the effects of ionizing radiation on tantalum oxide (TaOx) memristors. The data obtained from 60Co gamma ray and 10 keV X-ray ionizing radiation experiments indicate that it is possible for the devices to switch from a high resistance off-state to a low resistance on-state after a total ionizing dose (TID) step stress threshold has been surpassed. During irradiation, the devices were floating, grounded, or biased with a 1 Hz square wave with an amplitude of ±100 mV. While floating the terminals is not a typical bias condition within a circuit, it is speculated that this condition might be worst-case because of the lack of a discharge path. If a read measurement is performed prior to reaching the charge threshold, the devices 'reset' back to a pre-irradiation state. This suggests that the devices do not have a cumulative TID effect. However, it was observed that having a continuous bias on the device during the TID exposure did not always have the same effect. The TID threshold level at which the devices switch resistance states varies from device to device; the enhanced susceptibility observed in some devices is still under investigation. After a radiation-induced resistance change, all of the devices could be reset and still functioned properly. When the devices were set into a low resistance on-state prior to irradiation, there was not a significant variation in the resistance post-irradiation (i.e., the devices were still in the on-state). Overall, the memristor TID performance is promising and could potentially enable the discovery of a radiation-hardened nonvolatile memory technology to be used in space and aerospace applications. © 2014 IEEE.

Resistive random access memory (ReRAM), or memristors, may be capable of significantly improve the efficiency of neuromorphic computing, when used as a central component of an analog hardware accelerator. However, the significant electrical variation within a device and between devices degrades the maximum efficiency and accuracy which can be achieved by a ReRAMbased neuromorphic accelerator. In this report, the electrical variability is characterized, with a particular focus on that which is due to fundamental, intrinsic factors. Analytical and ab initio models are presented which offer some insight into the factors responsible for this variability.

A method for extracting interface trap density (DIT) from subthreshold I-V characteristics is used to analyze data on a SiC MOSFET stressed for thirty minutes at 175°C with a gate bias of-20 V. Without knowing the channel doping, the change in DIT can be calculated when referenced to an energy level correlated with the threshold voltage. © 2014 IEEE.

A method for extracting interface trap density (DIT) from subthreshold I-V characteristics is used to analyze data on a SiC MOSFET stressed for thirty minutes at 175°C with a gate bias of-20 V. Without knowing the channel doping, the change in DIT can be calculated when referenced to an energy level correlated with the threshold voltage. © 2014 IEEE.

A method for extracting interface trap density (DIT) from subthreshold I-V characteristics is used to analyze data on a SiC MOSFET stressed for thirty minutes at 175°C with a gate bias of-20 V. Without knowing the channel doping, the change in DIT can be calculated when referenced to an energy level correlated with the threshold voltage. © 2014 IEEE.

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