Comparative study on Cu ₂ZnSnS ₄ thin films deposited by sputtering and pulsed laser deposition from a single quaternary sulfide target

Cu ₂ZnSnS ₄ (CZTS) thin films were directly grown on the heating Mo-coated glass substrate by Sputtering and Pulsed Laser Deposition (PLD) with a single quaternary sulfide target. XRD and Raman scattering confirm that both CZTS films are of kesterite structure, although the composition of CZTS film deposited by Sputtering deviates from the stoichiometry of CZTS more significantly than that deposited by PLD. However, CZTS deposited by sputtering has poor crystallintiy and small grain-sizes in contrast with the sample deposited by PLD, due to severe compositional deviation. Reflection spectroscopy and spectroscopic ellipsometry demonstrate that these CZTS films have the ideal band gap (E _g≈1.5 eV) and high absorption coefficient as the absorber layer of thin-film solar cells. This implies that the optical properties of CZTS film are tolerant to its compositional deviation.