Modification of Schottky barrier height for NiFe/p-Si contacts by inserting an ultra-thin HfO2 dielectric layer

•Schottky barrier height of NiFe/HfO2/p-Si can be varied by altering HfO2 thickness.•Hf–O–Si bonds form at HfO2/p-Si interface and produce interface dipoles.•Surface energy band of p-Si bends downwards under dipole electric field.•Surface band bending downwards of p-Si leads to a rise in Schottky barrier height. The effects of HfO2 dielectric thickness (tHfO2) on the electrical properties of NiFe/HfO2/p-Si contacts were explored, and the microstructure and interfacial products of the contacts were analyzed. The results showed that Hf-O-Si bonds probably form at HfO2/p-Si interface and produce interface dipoles, and the number of the dipoles is positively linked to tHfO2. As tHfO2 grows from 0.5 to 1.5 nm, the enhanced dipole electric field will let the surface electric field of p-Si strengthen and the surface band of p-Si bend downwards, thus causing a rise in Schottky barrier height of the contacts and a dip in electric current.