(Invited) Pluse Plating for Compound Semiconductor Electrodeposition

Work in this group has mostly involved development of the electrochemical version of atomic layer deposition (E-ALD) over the last many years.  ALD refers to is a group of methods for the formation of materials an atomic layer at a time using surface limited reactions.   E-ALD achieves atomic level control during electrodeposition by alternating solutions and using underpotential deposition (UPD) to limit deposits to an atomic layer each cycle. It has been shown to form high quality deposits for a range of materials central to thin film photovoltaic formation, including: CdTe, CdS, CIS, and CIGS.  Growth chemistry for a family of absorber materials referred to as CZTS, or Cu₂ZnSn(S,Se)₄ is presently being investigated.  The primary advantages of CZTS for PV are that they are made from nontoxic earth abundant elements.  The primary advantage of an E-ALD process would be atomic layer control and conformal deposition. The main disadvantage would be the time it takes to grow a µm thick absorber layer.  The rate of growth is presently limited by the time it takes to alternate solutions.

Recently, efforts by this group have involved development of a variant of E-ALD based on potential changes (pulses), rather than solution exchanges, greatly increasing the rate of deposition.   Presently, this group refers to this method as potential pulse ALD (PP-ALD).   Preliminary results on the formation of Cu₂Se and other components of a CZTS absorber layer will be discussed.