Laboratory of Semiconductor Devices Kiev Shevchenko University

Activity of Laboratory of Semiconductor Devices concerns with the research and development of various chemical sensors based on new and promising semiconductor materials, including nanostructured and porous silicon, polymers, metal-oxides. Main detection principle based on the measurement of voltage-current, capacity-voltage, current-time characteristics of surface–barrier semiconductor structures or MIS devices with superthin metal (for example, catalytic metals films) as the transducer of gas environment and sponge –like interface layer (e.g. porous silicon). The using of island–type barrier metal film and sponge-like semiconductor allows to improve the sensitivity and selectivity of elaborated sensors.

The current activity includes:

the studying of the charge carrier transport in the nanocrystaline and porous silicon;

- the exploitation of nanocrystaline silicon /metal contact structures as basic sensing devices for principal gas pollutants : CO, NO2, CO2, SO2, hydrogen contained gases, etc;
- the modification of nanocrystaline silicon surface morphology by technique of i) the layer-by-layer deposition of organic/non organic/ compounds, ii) the metal introduction into the pore, iii) the deposition of catalytic metal from colloidal solutions;
- the theoretical and experimental analysis of absorption desorption processes 9andspecific surface reactions for chosen pollutants (gases, liquids), the definition of nanocrystaline silicon sensitivity to adsorbed molecules;
- e optimization of laboratory technology of manufacturing of nanocrystaline silicon/metal contacts, design of sensors’ topology;
- the theoretical and experimental analysis of I-V and C-V (impedance), luminescent, optical, spin-dependent and DLTS characteristics;
- design of gas sensing layers with different transducer principles and microsystems analyze devices, studying of the sensitivity and selectivity sensors arrays operated in variable conditions.

sensors of hydrogen contained gases

Sensors is based on Schottky contact of Pd(Pt)- porous silicon- p(n)-Si type, the range of measured values- 100-10000 ppm. The registration methods: impedance characteristics, voltage- currents and contact potential difference. The using of Pd or Pt catalytic metal on developed semiconductor surface allows to reduce the work in temperature from 500-6000? to 25 C.

Fig.1 Steady-state response of Pd/PS/p-Si (1), Pd/p-Si (2) and Pd/SiO₂/p-Si (3) structures versus hydrogen concentration.

Fig.2 Kinetics of the contact potential difference of Pd/PS/n-Si sensor under successive two cycles of 600 ppm H₂ concentration in synthetic air.