Dr Yazid Bouznit is a researcher at the Laboratory of Materials Study, Jijel University. He is the first author of the paper that won the 2014 Algerian Paper of the Year Award in Physical Sciences and Mathematics entitled “New co-spray way to synthesize high quality ZnS films” and which was published in the journal Applied Surface Science. Inspire magazine speaks to Dr Bouznit about the work reported in the award winning paper.
Inspire Magazine: Thank you for speaking to Inspire Magazine, and many congratulations for winning the 2014 Algerian Paper of the Year Award in Physical Sciences & Mathematics. How do you feel about winning this award?
Dr. Bouznit: Winning the 2014 Algerian Paper of the Year Award in Physical Sciences & Mathematics is really important. So, we feel honoured to receive such an award. The award is much more than a certificate or a piece of glass; it’s not the physical award that is important but rather the recognition of all the efforts we have put into the awarded study.
IM: In simple terms, can you tell us what the winning paper is about?
Dr. Bouznit: Our published paper reports on the elaboration of ZnS films via a new approach which is called co-spray method using zinc acetate dihydrate (Zn (CH3COO)2.2H2O) and thiourea (CH4N2S) precursors (the starting compounds from which the ZnS films will be made). We have investigated the effect of zinc to sulfur atomic ratios, i.e. the zinc content relative to sulfur levels.
IM: What are Zinc Sulfide films and why are they difficult to synthesis?
Dr. Bouznit: Zinc sulfide (ZnS) belongs to binary II-VI compounds (compounds or materials synthesised from chemical elements belonging to columns 2B and 6A of the periodic table), it is by far one of the most interesting semiconductor materials with a direct band gap of 3.68 eV at room temperature and 40 meV as exciton binding energy. The famous Rutherford’s Gold Foil Experiment in 1909 thoroughly documented the organization of the atom. The experience consisted of pointing a beam of alpha particles at a thin foil of metal (Gold) and measured the scattering pattern by using a fluorescent screen. The screen used to observe the alpha particle impact was made of zinc sulphide. The first crystallographic structure ever known is that of ZnS. The following are few examples of some application fields of this fascinating material:
Highly crystalline ZnS film is difficult to obtain using classical spray techniques (the obtained films are either cubic polycrystalline or amorphous which experimentally demonstrate less luminescence interest properties compared to the hexagonal analogue).
IM: Your award winning paper describes a method for addressing this difficulty; can you give us more details about this method?
Dr. Bouznit: Briefly, we have opened a new window allowing the achievement of high quality ZnS films. The method is a derivative of spray method, which is characterized by the much higher deposition yield, convenient handling and good repeatability compared with the previous spray configurations. In a typical spray route, one solution containing all the constituents being used to supply the desired material is atomized over a substrate heated to an adequate temperature. In our configuration, we used two independent solutions, atomized separately in the same manner.
IM: How is the co-spraying method you developed different from existing work in the literature and what advantages does it present in comparison to other methods?
Dr. Bouznit: Remarkably, with all designs available to fabricate ZnS films using spray way, zinc chloride has been the precursor mostly widely used to supply zinc cations. This is supported by numerous lines of investigation reported in literature on the elaboration of ZnS thin films, which accounts for us adopting the same arrangement for spray route.
There are two types of precursor solutions to prepare ZnS films. One is called cationic solution; the other is anionic solution. The primary difference between this method and the classical spray techniques is the presence of two independent solutions. In our work, zinc acetate dihydrate (Zn (CH3COO)2.2H2O) and thiourea (CH4N2S) were used as the starting salts to supply Zn2+ and S2- ions respectively. As you may know, the final properties of ZnS films (like other materials) strongly depend on the preparation method. In this regards, co-spray has proven itself as a powerful technique for preparing high quality ZnS films.
IM: What kind of application areas can your findings be applied to, and how would this apply specifically to Algeria?
Dr. Bouznit: Zinc sulfide is a well known phosphor material. It has numerous applications in optoelectronic devices such as solar cells. Algeria is at the forefront of countries calling to produce clean energy owing to the huge potential reserves that it provides. So, it is important to think about such material, by acquiring new knowledge, since it serves as part of solar cell devices.
Demand for energy from renewable resources is expected to rise in the next few decades. Algeria can develop new products with lower energy consumption. It can also identify new materials which reduce the cost of solar panels, windmills and batteries while making them more efficient, to reduce wastage and improve access to green technologies.
IM: Can you tell us about the kind of support that you have received to accomplish this work?
Dr. Bouznit: It has to be conceded that enormous individual efforts from specific personnel have been made to accomplish this work. We have received assistance from Algeria and countries such as China and South of Korea (particularly in the characterization of our samples). Real coordination and collaboration between researchers or even between countries is absolutely paramount.
IM: How does this work fit with other work done in your lab?
Dr. Bouznit: This is just a beginning and as you may know, scientific work is only one link in a long chain. Personally, I do not believe in physical boundaries (borders) between countries and nations (the same goes for laboratories) and in fact, there are no borders in scientific ventures. We live in the globalisation era where we are in contact with people from very diverse cultural backgrounds and possess diverse ideas and initiatives. Currently, we are working in this direction (thin films elaboration and characterization), but we look forward to use these elaborated films in other purposes or domains.
IM: What is your take on the general state of surface treatment research in Algeria?
Dr. Bouznit: We are looking at the emergence of this domain in our country and there is a great need to pay more attention to the importance of this field. There is a need for us to overcome our parochial physical borders and think more universally.
IM: Thank you again for speaking to Inspire Magazine and all the best with your future endeavors.
Dr. Bouznit: Thank you so much.