Matching Items (2)
Description
ABSTRACT
Programmable metallization cell (PMC) technology uses the mechanism of metal ion transport in solid electrolytes and electrochemical redox reactions to form metallic electrodeposits. When a positive bias is applied from anode to cathode, atoms at the anode are oxidized to ions and dissolve in the solid electrolyte. They travel to the cathode under the influence of an electric field, where they are reduced to form electrodeposits. These electrodeposits are filamentary in nature and grow in different patterns. Devices that make use of the principle of filament growth have applications in memory, RF switching, and hardware security.
The solid electrolyte under investigation is tungsten trioxide with copper deposited on top. For a standard PMC, these layers are heated in a convection oven to dope the electrolyte. Once the heating process is completed, electrodes are deposited on top of the electrolyte and biased to grow the filaments. What is investigated is the rate of dendritic growth to applied field on the PMC and the composition of the electrolyte. Also investigated are modified three-terminal PMC capacitance change devices. These devices have a buried sensing electrode that senses the increasing capacitance as the filaments grow and increase the upper electrode area.
The rate of dendritic growth in the tungsten trioxide and copper electrolyte of different chemistries and applied field to the PMC devices is the important parameter. The rate of dendritic growth is related to the change of capacitance. Through sensing the change in capacitance over time the modified PMC device will function as an odometer device that can be attached to chips. The attachment of these devices to chips, help in preventing illegal recycling of old chips by marking those chips as old. This will prevent would-be attackers from inserting modified chips in systems that will enable them to by-pass any software security precautions.
Programmable metallization cell (PMC) technology uses the mechanism of metal ion transport in solid electrolytes and electrochemical redox reactions to form metallic electrodeposits. When a positive bias is applied from anode to cathode, atoms at the anode are oxidized to ions and dissolve in the solid electrolyte. They travel to the cathode under the influence of an electric field, where they are reduced to form electrodeposits. These electrodeposits are filamentary in nature and grow in different patterns. Devices that make use of the principle of filament growth have applications in memory, RF switching, and hardware security.
The solid electrolyte under investigation is tungsten trioxide with copper deposited on top. For a standard PMC, these layers are heated in a convection oven to dope the electrolyte. Once the heating process is completed, electrodes are deposited on top of the electrolyte and biased to grow the filaments. What is investigated is the rate of dendritic growth to applied field on the PMC and the composition of the electrolyte. Also investigated are modified three-terminal PMC capacitance change devices. These devices have a buried sensing electrode that senses the increasing capacitance as the filaments grow and increase the upper electrode area.
The rate of dendritic growth in the tungsten trioxide and copper electrolyte of different chemistries and applied field to the PMC devices is the important parameter. The rate of dendritic growth is related to the change of capacitance. Through sensing the change in capacitance over time the modified PMC device will function as an odometer device that can be attached to chips. The attachment of these devices to chips, help in preventing illegal recycling of old chips by marking those chips as old. This will prevent would-be attackers from inserting modified chips in systems that will enable them to by-pass any software security precautions.
ContributorsKrishnan, Anand (Author) / Kozicki, Michael N (Thesis advisor) / Barnaby, Hugh J (Committee member) / Gonzalez-Velo, Yago (Committee member) / Arizona State University (Publisher)
Created2019
Tungsten Trioxide-based Variable Reflectivity Radiation Coatings for Optical Propulsion Applications
Description
This thesis explores the potential application of the phase change material tungsten trioxide (WO3) in optical force modulation for spacecraft and satellites. It starts with a literature review of past space optical force applications as well as potential phase change materials for optical force modulation. This is followed by the theoretical model and discussions of the optical properties of a variety of materials used in the structures explored thereafter. Four planar structures were analyzed in detail. Two of the structures were opaque and the other two were semi-transparent.
The first of the opaque structures was a tungsten trioxide film on aluminum substrate (WO3/Al). It was found to have a 26% relative change in radiation pressure with WO3 thickness of 200 nm. The second opaque structure was a tungsten trioxide film on silicon spacer on aluminum substrate (WO3/Si/Al). This structure was found to have a 25% relative change in radiation pressure with 180 nm WO3 and 20 nm Si.
The semitransparent structures were tungsten trioxide film on undoped silicone substrate (WO3/Si), and a tungsten trioxide film on a silicone spacer on tungsten trioxide (WO3/Si/WO3). The WO3/Si structure was found to have an 8% relative change in radiation pressure with 200 nm WO3 and 50 nm Si. The WO3/Si/WO3 structure had a relative change in radiation pressure of 20% with 85 nm WO3 and 90 nm Si.
These structures show promise for attitude control in future solar sailing space missions. The IKAROS mission proved the functionality of using phase change material in order to steer a space craft. This was accomplished with a 7.8% relative change in radiation pressure. However, this only occurred at a pressure change of 0.11 µN/m2 over a range of 0.4 to 1.0 µm which is approximately 77.1% of the solar spectrum energy. The proposed structure (WO3/Al) with a 26% relative change in radiation pressure with a pressure change of 1.4 µN/m2 over a range 0.4 to 1.6 µm which is approximately 80% of the solar spectrum energy. The magnitude of radiation pressure variation in this study exceeds that used on the IKAROS, showing applicability for future mission.
The first of the opaque structures was a tungsten trioxide film on aluminum substrate (WO3/Al). It was found to have a 26% relative change in radiation pressure with WO3 thickness of 200 nm. The second opaque structure was a tungsten trioxide film on silicon spacer on aluminum substrate (WO3/Si/Al). This structure was found to have a 25% relative change in radiation pressure with 180 nm WO3 and 20 nm Si.
The semitransparent structures were tungsten trioxide film on undoped silicone substrate (WO3/Si), and a tungsten trioxide film on a silicone spacer on tungsten trioxide (WO3/Si/WO3). The WO3/Si structure was found to have an 8% relative change in radiation pressure with 200 nm WO3 and 50 nm Si. The WO3/Si/WO3 structure had a relative change in radiation pressure of 20% with 85 nm WO3 and 90 nm Si.
These structures show promise for attitude control in future solar sailing space missions. The IKAROS mission proved the functionality of using phase change material in order to steer a space craft. This was accomplished with a 7.8% relative change in radiation pressure. However, this only occurred at a pressure change of 0.11 µN/m2 over a range of 0.4 to 1.0 µm which is approximately 77.1% of the solar spectrum energy. The proposed structure (WO3/Al) with a 26% relative change in radiation pressure with a pressure change of 1.4 µN/m2 over a range 0.4 to 1.6 µm which is approximately 80% of the solar spectrum energy. The magnitude of radiation pressure variation in this study exceeds that used on the IKAROS, showing applicability for future mission.
ContributorsVlastos, Joseph Niko (Author) / Wang, Liping (Thesis advisor) / Wang, Robert (Committee member) / Calhoun, Ron (Committee member) / Arizona State University (Publisher)
Created2020