Search

The microstructure of Cu(In,Ga)Se2(CIGS) films deposited under low Se flux was studied using scanning electron microscopy, scanning Auger electron spectroscopy and high resolution and analytical electron microscopy. CIGS films were deposited on Mo coated soda-lime glass substrate using the "3-stage" process in which the Se flux used during the third stage was restricted to a forth of standard value. In the as-grown CIGS films, voids were observed along the grain boundaries and a Cu2Se phase was identified at the surface and the grain boundaries. The voids and Cu2Se layer were produced by vaporization of an In-Se compound from the films during the third stage of deposition. A reaction model on the CIGS grain surface is proposed based on the microstructure observations.

MoSe2layers formed at the interface between Cu-In-Ga-Se and Mo layers were studied by X-ray diffraction and high resolution transmission electron microscopy. Various composition Cu-In-Ga-Se films such as Se, Cu-Se, In-Ga-Se and Cu-rich Cu-In-Ga-Se were deposited on Mo coated glass substrates by physical vapor deposition. For the case of the Se/Mo interface, a MoSe2layer of about 100 Å thickness was observed. The c-axis of the MoSe2grains were found to be oriented normal to the surface of Mo layer. For the Cu-Se/Mo and Cu-rich Cu-In-Ga-Se/Mo structures, the thickness of the MoSe2layers found at the interface was thin. For the case of the In-Ga-Se/Mo structure, a 0.1 µm thick interfacial MoSe2layer was observed whose c-axis was oriented parallel to the Mo surface. The microstructure of the In-Ga-Se/Mo film was similar to that of the device quality CIGS/Mo structure deposited by the "3-stage" process. A formation mechanism for the MoSe2layers occurring during the "3-stage" process is proposed.

SrxBa1-xNb2O6(0.2 ?x?0.4: SBN) ceramics were fabricated by pressureless sintering with the addition of V2O5(1 mol%) which considerably accelerated grain growth. X-ray diffraction analysis of elongated grains indicated that there is a morphotropic phase boundary between x=0.25 (tetragonal) and x=0.225 (orthorhombic) in the SBN system. The sharpening of a ferroelectric phase transition peak was maximum at x=0.2. This corresponded to a cation distribution in which the A2-sites in the tungsten bronze structure were fully occupied by Ba2+ions. A phase transition temperature diagram was developed for the present composition region.