Recent paper: Nanoscale piezoelectric surface modulation for adaptive extreme ultraviolet and soft x-ray optics

Our recent paper “Nanoscale piezoelectric surface modulation for adaptive extreme ultraviolet and soft x-ray optics” is now available online. In this work, we report fabrication of a piezoelectric based functional actuator with gradual surface modulation intended for wavefront correction at extreme ultraviolet (XUV) and soft x-ray (SXR) wavelengths for the first time.

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Abstract: Extreme ultraviolet and soft x-ray wavelengths have ever-increasing applications in photolithography, imaging, and spectroscopy. Adaptive schemes for wavefront correction at such a short wavelength range have recently gained much attention. In this Letter we report, to the best of our knowledge, the first demonstration of a functional actuator based on piezoelectric thin films. We introduce a new approach that allows producing a gradually varying surface deformation. White light interferometery is used to show the level of control in generating arbitrary surface profiles at the nanoscale.

Laser processing and chemistry

Laser processing and chemistry written by Prof. Dr. Dieter Bäuerle published by Springer is one of my favorite books. The book gives an overview of the fundamentals and applications of laser-matter interactions, in particular with regard to laser material processing. It is a heavy book with 32 chapters and covers the theoretical and fundamental discussions, and presents many experimental examples. Not to mention that it has very useful appendixes on different types of lasers and relevant material’s parameters.

I believe, this is a book that should always be available at the desk, so one can check on plots, equations, or reviewing a specific topic in materials processing by lasers. It would also be an excellent choice for a masters or PhD level course in physics, chemistry, or materials science. For this purpose, depending on the situation, one may include just several of the chapters in the course schedule.

Compositional and structural properties of Cr-doped ZnS

The article entitled “Compositional and structural properties of pulsed laser deposited ZnS:Cr films” has been published in Applied Physics A: Materials and Processing. The article is available from the publication menu.

As you might know, ZnS:Cr is a proposed intermediate band material, and we have deposited it by pulsed laser deposition. In this recent article we present a detailed study of the properties of ZnS:Cr films. The purpose is to understand how the structure of ZnS changes when we incorporate high amount of Cr in the ZnS lattice. In addition, we have studied the chemistry and composition of the deposited films by X-ray photoelectron spectroscopy. The paper presents an elaborate XRD and TEM study, and this study can lead to a better understanding of the Cr energy levels in the ZnS bandgap.

Resonant photoemission spectroscopy for intermediate band materials

Our recent article entitled “Resonant photoemission spectroscopy for intermediate band materials” is published in Applied Physics Letters (107, 192104 (2015); doi: 10.1063/1.4935536):

We have studied Cr-doped ZnS films for application in intermediate band solar cells. The goal was to understand the origin of intermediate bands in doped ZnS. In the article, we show that the intermediate-band can be characterized using resonant photoemission spectroscopy, revealing the filling and specific orbital character of the states contributing to the resonant photoemission signal. The methodology can be widely extended to a large variety of materials, providing useful information towards engineering of high efficiency intermediate band solar cells and of other optoelectronic devices. More information are available in this presentation.

Recent publication: PLA and PLD of ZnS:Cr

Our recent article entitled “Pulsed laser ablation and deposition of ZnS:Cr” is published in Thin Solid Films and is available online.

The article is presenting a method by which various dopant concentrations can be achieved using a single target by pulsed laser deposition. Varying doping/composition range is normally not achieved using a single target in pulsed laser deposition. Therefore, the focus of the article is describing various aspects of the method, such as target ablation study.

In addition, Cr doped ZnS films with high Cr content have spintronic and solar cell applications, for example as a potential intermediate band material. Growth of ZnS:Cr films with very high Cr content (up to 5 at.%) has not been reported previously. In the article, we report the growth and characterization of such Cr doped ZnS films.

Here are the highlights of the article:

  • ZnS:Cr films (2-5 %) were deposited by pulsed laser deposition using a single target.
  • Both the laser fluence and target pre-ablation affects the dopant concentration.
  • The non-stoichiometric transfer was controlled in a reproducible manner.


Recent publication

Our recent article entitled “Molecular beam and pulsed laser deposition of ZnS:Cr for intermediate band solar cells” is now published in Solar Energy Materials & Solar Cells (Read the paper here). Here are the highlights of the paper:


  • Cr-doped ZnS (ZnS:Cr) thin films with up to 7.5 at.% Cr, deposited by PLD and MBE are compared.
  • The highly doped Cr:ZnS films were made for use in intermediate band solar cells.
  • Similar optical properties, but different structural properties were achieved.
  • The sub-bandgap absorption increased linearly with Cr concentration.
  • Smoother and more textured films were obtained by PLD, compared to MBE.

Keywords: Pulsed laser deposition; Molecular beam epitaxy; Optical properties; Intermediate band solar cell; Doping and alloying; Transition-metal-doped semiconductor


Conference on II-VI compounds

I am going to participate in the 17th international conference on II-VI compounds and related materials, and will present a work entitled “Highly Cr-doped ZnS for intermediate band solar cells”. The conference will be held in Paris between 13 to 18th of September 2015. I would be glad to meet people working on growth and characterization of un-doped and doped ZnS and other II-VI compounds.

The Scope of the conference (from conference website)

The II-VI compounds provide a variety of unique optical, electrical and magnetic properties. The Conference will then cover all the aspects of basic and applied research, laying special emphasis on unique physical and material properties of II-VI compounds, related materials and nanostructures. A particular attention will be given to new trends and pioneering directions, as well as to new materials and devices.

The conference will give also the opportunity to review the most important achievements in practical applications of II-VI compounds in mid-infrared, visible and UV range detectors, optoelectronic devices…

It is an international forum aimed to review and stimulate the progress in basic and applied research on II-VI semiconductors and related materials, to facilitate the exchange of new ideas and to establish new scientific contacts.

Welcome to my blog

Welcome to my blog and academic homepage. I will use this blog to report on research activities, interesting ideas, news and scientific publications.  There will be more posts on renewable energy and solar cells in particular, as well as materials physics and condensed matter physics. I will also share some experience on how to enhance productivity, particularly in a scientific career.

I hope my blog can ease communication between me and other people with the same research interests. So I invite you to share your opinions, comments, links to interesting resources, etc. Your feedback would keep me motivated to update the blog frequently.