TiAl-based Ohmic Contacts to p-type 4H-SiC

This paper describes successfully formed ohmic contacts to p-type 4H-SiC based on titanium-aluminum alloys. Four different metallization structures were examined, varying in aluminum layer thickness (25, 50, 75, 100 nm) and with constant thickness of the titanium layer (50 nm). Structures were annealed within the temperature range of 800°C - 1100°C and then electrically characterized. The best electrical parameters and linear, ohmic character of contacts demonstrated structures with Al layer thickness equal or greater than that of Ti layer and annealed at temperatures of 1000°C or higher

Influence of multiple cleaning on the detection capabilities of ISFET structures

The method of cleaning the ISFET structures after application of a biological substance was developed. There are few references in the literature to cleaning methods of this type of structure for biological applications, but they are relatively complex and difficult to automate. We decided to use resources commonly available in technological laboratories and methods that could be relatively easily automated, which would enable the full potential of ISFET transistors to be used. During the experiments, both acetone and deionized water were tested. The cleaning method was modified and it was checked whether it is possible to use such a method on one transistor more than once and how it affects the transistor's detection capabilities. We managed to obtain an effective method of cleaning ISFETs from biological substances. This method does not allow for obtaining exactly the same state as the original state of the transistor, but it ensures its correct operation and determining the influence of the tested biological substance on the transistor based on the results

Tailoring Refractive Index and Adlayer Sensitivity of an Optical Fiber Fabry-Perot Interferometer by a Thin Layer Deposition

This work discusses the capability of tailoring sensitivity of an optical-fiber-based Fabry–Perot interferometric (FPI) sensor to changes in refractive index (volume) and formation of a layer on the sensor surface (adlayer). A simple single-layer approach shows some disadvantages, especially when refractive index (n) sensing is considered, e.g., there is no shift of the interference pattern in the wavelength domain. The considered FPI sensor is based on two transparent thin films deposited on a single-mode optical fiber’s end face. As the first layer, a high-n titanium oxide (TiO2) was chosen. We show that addition of a second layer of lower n results in the blueshift of spectral pattern with external n (next). Moreover, when an additional layer, e.g., biological one, is formed, a redshift of the pattern appears, what is in contrary to the shift induced by the increase of next. Numerical analysis as well as experiments show that a wide range of materials (with different n and thickness) can be applied as the second layer, influencing both volume and adlayer sensitivities. We have found that when the second layer thickness is tailored to obtain a well spectrally defined pattern, high n contrast between the layers increases the volume sensitivity, while for the moderate n contrast the adlayer sensitivity of the FPI can be enhanced. The proposed approach shows large tuning capability towards desired application, as well as can be easily introduced to large-scale sensor manufacturing. </p