Digitally alloyed ZnO and TiO2 thin film thermistors by atomic layer deposition for uncooled microbolometer applications

The authors demonstrate the digital alloying of ZnO and TiO2 via atomic layer deposition method to be utilized as the active material of uncooled microbolometers. Depositions are carried out at 200 °C. Crystallinity of the material is shown to be degraded with the increase of the Ti content in the grown film. A maximum temperature coefficient of resistance (TCR) of −5.96%/K is obtained with the films containing 12.2 at. % Ti, and the obtained TCR value is shown to be temperature insensitive in the 15-22 °C, thereby allowing a wide range of operation temperatures for the low cost microbolometers. © 2017 American Vacuum Society

Atomic layer deposition synthesized TiOx thin films and their application as microbolometer active materials

This paper demonstrates the possible usage of TiOx thin films synthesized by atomic layer deposition as a microbolometer active material. Thin film electrical resistance is investigated as a function of thermal annealing. It is found that the temperature coefficient of resistance values can be controlled by coating/annealing processes, and the value as high as -9%/K near room temperature is obtained. The noise properties of TiOx films are characterized. It is shown that TiOx films grown by atomic layer deposition technique could have a significant potential to be used as a new active material for microbolometer-based applications. © 2016 American Vacuum Society

LWIR all-atomic layer deposition ZnO bilayer microbolometer for thermal imaging

We propose an all-ZnO bilayer microbolometer, operating in the long-wave infrared regime that can be implemented by consecutive atomic layer deposition growth steps. Bilayer design of the bolometer provides very high absorption coefficients compared to the same thickness of a single ZnO layer. High absorptivity of the bilayer structure enables higher performance (lower noise equivalent temperature difference and time constant values) compared to single-layer structure. We observe these results computationally by conducting both optical and thermal simulations. © 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

An analysis for the broad-band absorption enhancement using plasmonic structures on uncooled infrared detector pixels

This paper introduces an analysis on the absorption enhancement in uncooled infrared pixels using resonant plasmon modes in metal structures, and it reports, for the first time in literature, broad-band absorption enhancement using integrated plasmonic structures in microbolometers for unpolarized long-wave IR detection. Different plasmonic structures are designed and simulated on a stack of layers, namely gold, polyimide, and silicon nitride in order to enhance absorption at the long-wave infrared. The simulated structures are fabricated, and the reflectance measurements are conducted using an FTIR Ellipsometer in the 8-12 μm wavelength range. Finite difference time domain (FDTD) simulations are compared to experimental measurement results. Computational and experimental results show similar spectral reflection trends, verifying broad-band absorption enhancement in the spectral range of interest. Moreover, this paper computationally investigates pixel-wise absorption enhancement by plasmonic structures integrated with microbolometer pixels using the FDTD method. Special attention is given during the design to be able to implement the integrated plasmonic structures with the microbolometers without a need to modify the pre-determined microbolometer process flow. The optimized structure with plasmonic layer absorbs 84 % of the unpolarized radiation in the 8-12 μm spectral range on the average, which is a 22 % increase compared to a reference structure with no plasmonic design. Further improvement may be possible by designing multiply coupled resonant structures. © 2012 SPIE