Sputter-deposited ZnO and reactivity of ZnO/Ti interfaces

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Date and time 07.12.2015 13:1514:15  
Place and room
Speaker Dr. Sergey Grachev, Laboratoire Surfaces du Verre et Interfaces (SVI), Saint-Gobain France
Category Conferences - Seminars
Saint-Gobain has been producing glass for 350 years. Application of transparent multilayers on glass is the principle way to alter and add properties to glass: conductive, optical, mechanical and others. Magnetron sputtering for film’s deposition is the method of choice in industry due to its high deposition rates, homogeneity of the deposit, and its flexibility to adjust to a very wide range of materials. One of the important products of Saint-Gobain is low-emissive window glass, based on Ag films for thermal isolation of buildings by effective reflecting the IR radiation. Such low-e stacks are composed of an ultrathin film of Ag, a ZnO layer used as a substrate for silver growth and, in some cases, a few nm of Ti in between as adhesion enhancer.

ZnO is a piezoelectric semiconductor composed of alternating planes of Zn2+ and O2– in the c-direction of the lattice. Thus the (0001) surface can be Zn- or O-terminated. These two surfaces have in fact rather different properties. The two surfaces can be identified by a feature in the band structure attained with X-ray photoelectron spectroscopy (XPS). We managed to control the orientation of the sputter-deposited ZnO films by applying a potential to the substrate during deposition. It appeared that the preferential orientation can be managed only in a narrow range of temperatures.

In contact with Ti, ZnO films, nominally, form an Ohmic contact. However, the chemical reactivity can play an important role at such interfaces. We have studied ZnO/Ti interfaces by high energy XPS (HAXPES) at Bessy II synchrotron. This technique, contrary to conventional XPS, allows for photoelectron detection from buried (down to 30 nm) interfaces due to their longer mean free path. We managed to follow the chemical reaction in ZnO/Ti films during annealing. It results in oxidation of Ti, appearance of metallic Zn and its diffusion to the surface and consequent evaporation. We showed that deposition conditions of ZnO impact its stability in such chemical reaction.

Bio: Sergey Grachev
1990 – 1996: Department of Solid State Physics, Faculty of Experimental and Theoretical Physics at Moscow Engineering Physics Institute (State University).
1996 – 1998: PhDstudent at the Institute for Nuclear Research (Moscow), Russian Academy of Sciences, “Effect of oxygen doping in YBaCuO studied by inelastic magnetic neutron scattering” (not finished)
1998 – 2003: PhDstudent at University of Groningen. PhD thesis: “Manipulation and control of growth of magnetic iron nitride films”.
2003 – 2006:  PostDoc researcher at the Netherlands Institute for Metals Research (Delft), “Microstructure of- and stress in- PVD Cr coatings”.
2006 – current Surface du verre et interfaces, CNRS/Saint-Gobain, Saint-Gobain Recherche, Aubervilliers, France

Practical information

  • General public
  • Free

Organizer

  • Fabien Sorin

Contact

  • Fabien Sorin

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