Technical Abstract: Wide Band Gap (WBG) semiconductor-based devices are capable of operating in extreme environmental conditions such as high temperatures, high radiation and reactive environments because of the intrinsic properties of the semiconductors. However, usual contacts and interconnects will fail long before the semiconductor fails in harsh environments. One of the goals of the research is to explore refractory metals, their alloys and silicides as oxidation and diffusion barrier layers to protect contacts on WBG semiconductor-based devices. This major research instrumentation award will fund the acquisition of a sputtering system at Elizabeth City State University. The sputtering system will be used to deposit high temperature barrier material in vacuum. The effectiveness and reliability of the device will depend interfacial reactions (including oxygen defects and mobility or accumulation of carbon) between vacuum sputtered barrier layer (< 100 nm thick) and contacts on WBG semiconductors (SiC, GaN, and Diamond). To physically characterize interface reactions at elevated temperatures, Rutherford Backscattering Spectrometry (RBS), Auger Electron Spectroscopy (AES), and Electron Microscopy (TEM & SEM) will be employed. The stability of the electrical characteristics of a simple schottky device will indicate the effectiveness of the barrier layer in harsh environment. Access to a sputtering system will also enable us to explore new collaborations with the center for materials research at Norfolk State University and Varicon Inc. in the field of "smart windows" for efficient energy use in buildings. For this and similar applications, solar materials called chromogenic materials (mostly doped transition metal oxide) will be deposited with the sputtering system and characterized locally and by collaborators.
This major research instrumentation award funds the acquisition of a sputtering system at Elizabeth City State University. The sputtering system will be used to deposit high temperature metallic nano-layers (layers with thickness of about one-thousandth the thickness of human hair) in vacuum. The metallic nano-layers will be explored as barrier layer to protect devices fabricated on Wide Band Gap (WBG) semiconductors (SiC, GaN, Diamond, etc). These semiconductors have intrinsic properties that make them capable of surviving in harsh environmental conditions such as high temperature, high radiation and reactive environment. However, usual contacts will fail readily under extreme environmental conditions if not protected, limiting the WBG semiconductor-based device capability. Specialized electronic devices (including high power switches, sensors, controls and power management for aerospace and automotive industries) capable of operating at such extreme conditions can be located inside automobile engine block for more efficient fuel consumption and reduced atmospheric pollution (due to incomplete gas combustion). In ambient air at elevated temperature, reaction between adjacent layers in a composite contact metallization structure is one of the factors that will limit the reliability and effectiveness of WBG semiconductor-based devices. One of the primary goals is to study such reactions using state-of-the-art, high technology equipment for surface analysis. A simple schottky diode device with appropriate protective barrier layer will be evaluated in ambient air at high temperatures over an extended period of time. The stability of the devices electrical characteristics will imply the effectiveness of the barrier layer. Access to a sputtering system will also enable the team to explore new collaborations with the center for materials research at Norfolk State University and Varicon Inc. in the field of "smart windows" for efficient energy use in buildings. For this and similar applications, solar materials called chromogenic materials (mostly doped transition metal oxide) will be deposited with the sputtering system and characterized locally and by collaborators.
The goal of the Major Research Instrumentation grant is to acquire research equipment to establish or enhance faculty research, students’ research training and outreach activities. At ECSU, the goals of the MRI grant include the following: Goal1: To acquire, install and operate a magnetron sputtering system for materials research at Elizabeth City University (ECSU). Goal 2: To develop and evaluate barrier layers (less than 100 nm thick), as part of the sputter-deposited metallization scheme, that can protect important contact metal on electronic devices operating at an elevated temperature environment (> 500°C) for a long time (> 5000 hours). Goal 3: To investigate the optical properties (reflectance and transmittance) and optical switching in the wavelength region from mid-infrared to ultraviolet as a function of temperature in the environment. Goal 4: Engage undergraduate students at ECSU in collaborative material science research and education. Goal 5: Establish High School Summer Research Internship opportunities for local high school students in materials research activities. The two materials research projects established with this grant: Project 1: Focused on the development of contact metallization for Wide Band Gap (WBG)-based devices that will operate at an elevated temperature environment where a traditional silicon device cannot operate. We study the diffusion properties and effectiveness of sputter-deposited barrier layer (< 100 nm thick), as a part of the composite metallization structure for WBG semiconductor devices. Tantalum rich Ta-Si-N barrier layer was developed and its effectiveness evaluated over hundreds of hours on CVD diamond layer. This work was presented during the fall 2012 Materials Research Society Conference at Boston [1]. The metallization is still been evaluated on WBG based Schottky device, some of our results will be presented during the fall 2013 MRS conference. The abstract has been accepted. Project 2: Focused on depositing transition metal oxides on quartz substrates by reactive magnetron sputtering of transition metal targets in argon, oxygen and nitrogen gas mixtures.The goal of this project is to investigate the optical properties (reflectance and transmittance) and optical switching in the wavelength region from mid-infrared to ultraviolet as a function of temperature in the environment. Vanadium dioxide film that shows thermochromic characteristics have been produce in our research lab. Our research effort to reactively sputter vanadium dioxide films from vanadium target is yet to be successful. We reported some of the work on this project during the fall 2012 MRS conference in Boston [2]. Our abstract to present our recent success in this project was accepted for fall 2013 MRS conference. Important Outcomes and Achievements: Some of the results of this research have enabled the investigators to secure another NSF MRI funding to purchase SEM/EDS for further research/education activities. This instrument will broaden the materials research base at ECSU and encourage interdisciplinary and collaborative research within the university. As a result of the program advertisement at neighboring high schools and at ECSU, the physics program has 5 undergraduates (physics majors) in the university physics 1 course (PHYS 191) this fall 2013. The highest we have had in any one class since the PI joined the faculty at ECSU in 2007. Two articles were published based directly on the results from these projects in 2013. Two abstracts were submitted and accepted for the 2013 Fall Materials Research Society Conference. Seven (7) undergraduate students worked with the PI on these projects during the period of the grant. Majority of the students worked with the PI in the summer as well during the academic year. A total of twelve (12) high school students from neighboring schools worked with the PI and undergraduate students in the summer of 2012 and 2013. The students’ stipend was partly provided by this grant and the HBCU-UP RIA grant. The PI took two undergraduate students to fall 2012 MRS conference at Boston. It was their first exposure to international scientific conference and in fact it was their first time flying in airplane. The student presented their poster during the conference. It was a great experience for them and for the PI as well.
