Characterization of pyrolytic boron films

The transport mechanisms of pyrolytic B films were elucidated in order to study the characteristics of boron thermistors. Boron films were deposited thermal decomposition of BCl3 and H2 onto Mo (wires or sheets) of insulating (quartz) substrates. Electrical properties were studied for films in the thermistor structure with a layer bonded between two Mo crossed wires that formed electrical contacts, or films on quartz. The electrical conduction of the pyrolytic films was 7 × 10-5-10-6 Ohm-1 cm-1. An equation for the linear temperature dependence of the electrical conductivity is given for the temperature range 60-800 K. The thermoelectric power of the pyrolytic boron film was positive in the order 100 µV K-1 at 300 K. No appreciable photoconductiviy was observed. The results suggest that thermally activated hopping is the dominant transport mechanism in pyrolyic boron film. This film is superior to the crystalline or amorphous forms for the thermistor preparation.