Effect of Substrate Bias on the Structural and Electrical Properties of Sputtered Mo Thin Films on Flexible Substrates

The metal molybdenum (Mo) thin films deposited on flexible substrates can act as the contact electrode of flexible Cu(In, Ga)Se ₂ or Cu ₂ ZnSn(S,Se) ₄ solar cells. In this work, in order to enhance the structural and electrical characteristics of flexible Mo thin films, a negative substrate bias was applied during the direct current sputtering of Mo thin films. The flexible substrates used for growing the Mo films were stainless steel foils and polyimides. The characteristics of Mo thin films were studied by x-ray diffraction and sheet resistance measurements. The measured results reveal that an optimal value of negative substrate bias can be found for improving the electrical and structural characteristics of Mo thin films on flexible substrates. The minimum sheet resistances of Mo thin films are 2.50 Ω/sq and 2.73 Ω/sq for the stainless steel foil and polyimide substrates, respectively.