This Small Business Technology Transfer Phase I project aims to develop highly sensitive and inexpensive uncooled microbolometers using ultra-thin films of metals, metal oxides, or semi-metals. These microbolometers will be attractive for use in portable night vision devices and other thermal imaging applications that require a Noise Equivalent Temperature Difference (NETD) of less than 20 mK. We have already demonstrated metal microbolometers microfabricated from titanium thin films on SiO2/Si3N4/SiO2 cantilevers with a negative temperature coefficient of resistance (TCR) as high as - 0.67%/K (which is higher than that of bulk titanium films), with a NETD of approximately 18 mK and a 1/f noise lower than that of vanadium oxide films. The TCR can be further increased to values greater than 2%/K using alternative metals, metal oxides, or semimetals. Furthermore, thin film metallic or semimetallic microbolometers have low noise characteristics and other important advantages, including a simplified fabrication process and a lower manufacturing cost.
The broader impact/commercial potential of this project is to achieve low-cost and high-sensitivity infrared (IR) detection with uncooled microbolometers, which will allow the replacement of cooled IR detectors in some low-end military and civilian applications, including night vision, navigation, biological radiometry, target discrimination, spectroscopy, and thermal profiling. Microbolometers can be further scaled down to reduce each pixel?s thermal mass, allowing a faster response to a given amount of radiation, while maintaining or improving mechanical strength. By exploring other ultra-thin film materials for uncooled IR detectors, the manufacturing cost, reliability, and uniformity can be further improved during the fabrication process. This research work will also help us further understand the electrical, optical, mechanical and thermal properties of ultrathin films of metals and semimetals. The proposed activity broadens the participation of underrepresented groups, since senior research scientists involved belong to underrepresented groups. Undergraduate involvement in this project will enhance NSF?s educational goals. Finally, the results of this project will be disseminated through publications in scientific and industry journals.
During this Small Business Technology Transfer Program (STTR) Phase I project we developed a sensitive and inexpensive uncooled microbolometers using ultra-thin metal and metal oxide films (as small as 2 nm thick) in metal-insulator transition (MIT) regime. These microbolometers can be used for portable night vision device and other applications that require very high sensitivities. The sensitivity was increased greatly at these low thicknesses. Further, thin films have low noise characteristics and other important advantages, including simplified fabrication and a lower manufacturing cost. Metallic microbolometers also enable the use of alternative substrate materials for improved thermal isolation and better temperature resolution at the nanoscale. Uncooled infrared sensors can replace cooled sensors in many military and civilian applications, including night vision, navigation, biological radiometry, target discrimination, spectroscopy, thermal profiling, situational awareness, and persistent surveillance allowing these devices to enter general purpose commercial applications. Low cost, high performance nanobolometers can reduce a pixel’s thermal mass for faster response to a given amount of radiation while maintaining or improving mechanical strength. Uncooled microbolometers are currently used in the manufacture of highly specialized thermal imaging applications such as night vision and scanning thermal microscopy (SThM). In order to operate effectively, microbolometers must have a high temperature coefficient of resistance (TCR) and low noise characteristics. In addition, the materials used to manufacture microbolometers must be inexpensive and compatible with current CMOS processes. These are the primary conditions that have to be met as part of the continuing effort to develop even smaller, better performing microbolometers that weigh less and consume less power. An additional finding included the development of a novel technique to characterize and calibrate scanning bolometers. The proposed activity broadens the participation of underrepresented groups since a senior research scientists involved belong to underrepresented groups. Student involvement in this project enhanced NSF’s educational goals. Finally, the results of this proposal will be disseminated through publications in scientific journals.
