March 17, 2004 – IBM researchers have developed a method for making thin films of semiconducting materials that allow better mobility of electrical charges. Semiconducting materials made with the spin-coating technique typically have low mobility (conductivity of a material divided by the number of charges); the IBM team led by David Mitzi developed a way to dissolve materials with up to 10x better mobility.

The IBM team combined hydrazine with equal numbers of chalcogen atoms and semiconducting metal chalcogenide molecules (e.g. sulfur and tin sulfide) to improve solubility. Heating the film caused the hydrazine and sulfur to dissociate and evaporate, leaving a thin layer of metal chalcogenide with uniform thickness of about 5nm. Optimizing the procedure led to mobility approaching that of polycrystalline silicon, and 10x that of any previously spin-coated material and of amorphous silicon.

The scientists expect the technique will advance the use of low-cost processes such as spin coating, printing, stamping, nanoimprinting, inkjet printing, and dipping. Potential applications for the films include advanced displays, smart cards and RFID tags, sensors and photovoltaic solar cells, and phase-change solid-state memories.