Photonic crystals in biology - NanoTR-VI

PP forP forP edit.PPoster Session, Thursday, June 17Theme F686 - N1123Characterization of Sputtering Deposited AgGaSe2 Thin Films111UHakan KaraaaçUP P*, Mehmet ParlakP Pand Çidem ErçelebiP1PDepartment of Physics, Middle East Technical University, Ankara 06531, TurkeyAbstract- The single phase of AgGaSeR2R thin films were deposited onto soda-lime glass substrate by sequentially deposition of Ag and GaSeusing DC and RF sputtering. Physical properties were investigated by carrying out several type of measurements and the convenience of thismaterial to be used in the solar cell structure was determined.Nowadays, I-III-VIR2R ternary compounds have beenattracting considerable attention due to their interestingphysical properties. These compounds are regarded to be theternary analog of the II-VI binary materials. I-III-VIR2Rsemiconductors crystallize with the structure calledchalcopyrite being a super lattice of II-VI binary’s (zincblende) structure [1]. I-III-VIR2R ternary compounds arepotential candidates for photovoltaic applications [2], nonlinearoptics [3], light-emitting diodes [4], and frequencyconversation applications [5].AgGaSeR2R is a well-known ternary semiconductor. It’s ofparticular interest due to owing optical non-linear propertiesused in many applications like the generation of second andthird harmonic frequencies of COR2R laser output [6-8]. It is alsofound that AgGaSeR2R is a good candidate for the preparation ofschottky diodes [9], X- and Gamma-ray detector [10], andsolar cells [11].AgGaSeR2R thin films were deposited onto soda-lime glasssubstrates by a combination of DC and RF sputtering. Theoptimization of single layers of Ag and GaSe was performedby conducting several deposition cycles with the sameparameters before the sequentially deposition ofGaSe/Ag/GaSe/Ag/GaSe/Ag/GaSe/Ag/GaSe thin film layersonto soda-lime glass substrates kept at constant temperatureoaround 250 P PC to form AgGaSeR2R thin film.Results of energy dispersive analysis of X-rays (EDXA)indicated a Ga-rich composition and that there is aconsiderable effect of annealing temperature on variation inamount of constituent elements in AgGaSeR2R thin film. Thestructural analysis of the as-grown and films annealed betweenoo350 P PC and 600 P PC has been carried out by X-ray diffraction(XRD) measurements. Results revealed that all films arepolycrystalline in nature and Ag metallic phase exists in theamorphous AgGaSeR2R structure up to annealing temperatureoo450 P PC. When the annealing temperature raised to 600 P PC itwas observed that the Ag phase disappears perfectly and thestructure is consisting of single phase AgGaSeR2R with (112)preferred orientation. The crystalline sizes of the annealed filmoobetween 350 P PC and 600 P PC were calculated from the XRDmeasurements and compared with grain sizes measured fromthe recorded scanning electron microscopy (SEM)micrographs. In addition, from the lattice parameters found forAgGaSeR2R thin film, some structural anomalies parametersrelated to chalcopyrite compounds like anion displacementand tetragonal distortion parameters have been calculated andcompared with previously reported values.Optical properties of AgGaSeR2R thin films were studied bycarrying out transmittance and reflectance measurements inthe wavelength range of 325-1100 nm at room temperature.By using the obtained spectral data for transmittance andreflection, the absorption coefficient and optic band gap valuesfor as-grown and annealed samples were calculated. Thefound energy values indicated that AgGaSeR2R thin film showsthe characteristic optical structure related to I-III-VIR2Rchalcopyrite compounds. That’s the crystal-field and spinorbitsplitting levels were resolved by observing band to band,the crystal-field to conduction band minimum, and spin-orbitlevel to conduction band minimum transitions withcharacteristic energy values reported previously. Thecalculated energy values for these transitions were found to be1.77 eV, 2.00 eV, and 2.25 eV, respectively for film annealedoat 550 P PC and there is a fair agreement with previouslyreported data. The levels originating from the crystal-field andspin-orbit interaction were also observed from thephotospectral response measurements with the almost sameenergy values obtained from the absorption measurements(1.77 eV, 2.00 eV, and 2.25 eV respectively for sampleoannealed at 550 P PC).Finally, the temperature dependent conductivity and Halleffect measurements were carried out in the temperature rangeoof 100-430 K for as-grown and film annealed at 450 P PC ando550 P PC. The electrical resistivity of the films was in the rangeof 30-1000 -cm and indicated n-type conduction confirmedfrom the hot-probe and Hall effect measurements. Based onHall effect measurement results it is found that there isdecrease in mobility and increase in carrier concentrationfollowing to increasing annealing temperature. The room14temperature carrier concentration calculated to be 9.6x10P-315 -316 -3cmPP, 1.7x10PP cmPP, and 6.6x10PP cmP as-grown, filmsooannealed at 450 P PC and 550 P PC, respectively. The room2 -1temperature mobility values were found to be 6.4 cmP P (Vs)PP,2 -12 -13.7 cmP P (Vs)PP, and 3 cmP P (Vs)P as-grown and filmsooannealed at 450 P PC and 550 P PC, respectively.*Corresponding author: karaagac@metu.edu.tr[1] J. L. Shay, J. H. wernic, Ternary Chalcopyrite Semiconductors,Growth, Electronic Properties and Applications, Pergamon, Oxford,1975[2] L. L. Kazmerski, Nuovo Cimento D 2 (1983) 2013[3] B. F. Levine, Phys. Rev. B, 7 (1973) 2600[4] J. L. Shay, L. M. Schiavone, E. Buehier, J. H. Wernic, J. Appl.Phys. 43 (1972) 2805[5] F. K. Hopkius, Laser Focus World 31 (1995) 87[6] P. G. Schunemann, S. D. Setzler, T. M. Pollak, J. Cryst. Growth211 (2000) 257[7] G. C. Bhar, S. Das, D. V. Satyanarayan, P. K. Datta, U. Nundy,Y. N. Andreev, Opt. Lett. 15 (1995) 2057[8] E. Takaoka, K. Kato, Opt. Lett. 24 (1999) 902[9] P. Ribinson, J. I. B. Wilson, Inst. Phys. Conf. Ser. 35 (1977) 229rd[10] G. F. Knoll, Radiation detection and Measurement 3P(New-York; Willey), (1999)[11] Y. Satyanarayana Murty, O. M. Hussain, B. S. Naidu, P. J.Reddy, Mater. Lett. 10 (1987) 5046th Nanoscience and Nanotechnology Conference, zmir, 2010 754