A boron-doped Si0.8Ge0.2 thin film of 300 nm thickness was deposited by helicon sputtering. Thermal annealing was carried out to crystallize as-deposited amorphous-like Si0.8Ge0.2 thin films. The thermoelectric properties of the films, such as an electrical conductivity, a carrier concentration, a mobility, and a Seebeck coefficient, were investigated. As a result, the films by helicon sputtering exhibited finer grains and smoother surface than those of the film deposited by conventional radio frequency (rf) sputtering. The film deposited by helicon sputtering with an rf induction coil power of 50 W and annealed at 1100 degrees C for 5 h showed a resistivity of 0.011 Omega cm, a Seebeck coefficient of 0.13 mV/K, a Hall mobility of 9.92 cm(2)/V s, and a carrier concentration of 5.7 x 10(19) cm(-3) at 100 degrees C. A microthermoelectric hydrogen sensor (micro-THS) with the boron-doped Si0.8Ge0.2 thin film and annealed at 1100 degrees C for 5 h showed high sensitivity for hydrogen gas in air. This sensor could have wide detection range of hydrogen concentration from 1 ppm to 3%. At an operating temperature of 100 degrees C, for the low hydrogen concentration of 5 ppm, clear response was shown by the micro-THS with the Si0.8Ge0.2 film deposited by helicon sputtering and annealed at 1100 degrees C for 5 h. (c) 2006 The Electrochemical Society.