Influence of deposition rate of LaF3 and annealing on the capacitance–voltage (C–V) characteristics of LaF3/Si heterostructures

This article reports an investigation on the influence of deposition rate and annealing on the steepness of the capacitance–voltage (C–V) response of the LaF3/Si heterostructure to be used as a potentiometric fluoride (F–) sensor. With various deposition rate of 50, 60 and 95 nm/min, 145 nm (±5 nm)-thick LaF3 films were grown directly on the Si substrate. The C–V response of the LaF3/Si structures was obtained by an impedance analyzer at a frequency of 10 kHz. Later, the LaF3/Si structures were annealed in the air at 450 °C for 10 min and the investigations were repeated. The steepness of the C–V response of the as-deposited structures first increased with the increase in deposition rate until 60 nm/min and then started decreasing with the further increase in the deposition rate. The annealed structures always showed higher steepness than the as-deposited structures. Moreover, unlike the as-deposited structures the steepness of the C–V response always increased with the increase in deposition rate. The experimental results reveal that to design a LaF3/Si heterostructure having highest steepness the LaF3 should be deposited at a higher rate and then the LaF3/Si heterostructure should be annealed.