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ISSN: 0391 2051

ANNO LXVII LUGLIO-AGOSTO 2012 N. 4

ANNO LXVII LUGLIO-AGOSTO 2012 N. 4

A T T I DELLA «FONDAZIONE GIORGIO RONCHI»

EDITORIAL BOARD

Pubblicazione bimestrale - Prof. LAURA RONCHI ABBOZZO Direttore ResponsabileLa responsabilità per il contenuto degli articoli è unicamente degli Autori

Iscriz. nel Reg. stampa del Trib. di Firenze N. 681 - Decreto del Giudice Delegato in data 2-1-1953

Tip. L’Arcobaleno - Via Bolognese, 54 - Firenze - Agosto 2012

Prof. Roberto BuonannoOsservatorio Astronomico di RomaMonteporzio Catorne, Roma, Italy

Prof. Ercole M. GloriaVia Giunta Pisano 2, Pisa, Italy

Prof. Franco GoriDip. di Fisica, Università Roma IIIRoma, Italy

Prof. Vishal GoyalDepartment of Computer SciencePunjabi University, Patiala, Punjab, India

Prof. Enrique Hita VillaverdeDepartamento de OpticaUniversidad de Granada, Spain

Prof. Irving KaufmanDepartment of Electrical EngineeringArizona State University, TucsonArizona, U.S.A.

Prof. Franco LottiI.F.A.C. del CNR, Via Panciatichi 64Firenze, Italy

Prof. Tommaso MaccacaroDirettore Osservatorio Astronomico di Brera,Via Brera 28, Milano

Prof. Manuel MelgosaDepartamento de OpticaUniversidad de Granada, Spain

Prof. Alberto MeschiariScuola Normale Superiore, Pisa, Italy

Prof. Riccardo PratesiDipartimento di FisicaUniversità di Firenze, Sesto Fiorentino, Italy

Prof. Adolfo PazzagliClinical PsychologyProf. Emerito Università di Firenze

Prof. Edoardo ProverbioIstituto di Astronomia e Fisica SuperioreCagliari, Italy

Prof. Andrea RomoliGalileo Avionica, Campi BisenzioFirenze, Italy

Prof. Ovidio SalvettiI.ST.I. del CNRArea della Ricerca CNR di Pisa, Pisa, Italy.

Prof. Mahipal SinghDeputy Director, CFSL, Sector 36 AChandigarh, India

Prof. Marija StrojnikCentro de Investigaciones en OpticaLeon, Gto Mexico

Prof. Jean-Luc TissotULIS, Veurey Voroize, France

Prof. Paolo VanniProfessore Emerito di Chimica Medicadell’Università di Firenze

Prof. Sergio VillaniLatvia State University, Riga, Lettonia

γ-Radiation effects on some optical constants of CuS thin fi lms

NADIR FADHIL HABUBI (*), SAMI SALMAN CHIAD(*),FIRAS HASHEM AHMED (*), AMER SALIH MAHDI (**)

SUMMARY. – Thin fi lms of CuS have been prepared on a glass substrate using the chemical bath deposition technique. The effect of 137CS γ-radiation on some optical constants of CuS thin fi lms have been studied, it was found that the optical energy gap decreases after irradiation while re-fl ectance, refractive index, extinction coeffi cient, optical conductivity, real and imaginary parts of dielectric constant, increase after irradiation by γ-rays.

Key words: CuS, Optical constants, Chemical bath deposition, Thin fi lm

1. Introduction

P-type semiconductor CuxS thin fi lms have attracted wide attention, due to their interesting optical and electrical properties. Copper sulfi de has very complex crystal chemistry owing to its ability to form various stoichiomtric compounds (1). Mixture phases copper sulfi de can usually obtained in many synthetic routes, these are copper-rich phases exist as chalcocite (Cu2S). Djurlite, digenite, anilite and sulfur-rich phase exist as covelite (CuS) (2.3).

Covelite was attracted great interest for its potential use in many applications such as solar cell, photochemical conversion of solar energy as solar absorber coating (4), photoconductor, sensors (5,6), conductive electrodes (7), IR detector and catalyst (8.9).

Numerous techniques have been used to prepare thin fi lms of CuS such as high-temperature solution growth technique, spray pyrolysis, RF reactive sputter-ing and chemical bath deposition (10-13).

(*) Al_Mustansiriyah University, College of Education, Physics Department, Baghdad\ Iraq.

(**) Al_Mustansiriyah University, College of Science, Chemistry Department, Baghdad\ Iraq.

ATTI DELLA “FONDAZIONE GIORGIO RONCHI” ANNO LXVII, 2012 - N. 4

THIN FILMS

N.F. Habubi - S.S. Chiad - F.H. Ahmed - A.S. Mahdi594

The objective of this study was to explore the effect of γ-Rays from CS137 on the optical parameters of CuS thin fi lms. As it is known that exposure of these fi lms to γ-radiation is accompanied by the accumulation of irreversible structural damage, which results in signifi cant negative changes in the physical characteris-tics.

2. Experimental procedure

Glass microscope slide were cleaned by ultrasonic bath fi lled with ethanol, rinsed in distilled water and dried in air. Reaction bath were 100 ml glass beaker containing different molar solutions and volumes of deposition reagents. The de-position of CuS thin fi lms was based on the reaction between CuCl2.2H2O, and thiourea SC(NH2)2 using triethanolamine (TEA), sodium hydroxide and ammo-nia as a complexing agent.

Bath parameters including deposition time and PH were optimized. De-tailed of bath constituents are shown in Table 1.

Table 1The volumes of the materials used in CBD

Volume of TEA (ml)

Volume of CuCl2.2H2O (ml)

Volume of thiouera (ml)

Volume of Am-monia (ml)

Volume of NaOH ml

Volume of water ml

8 10 6 8 10 58

The clean glass substrates were then placed vertically inside the beaker with-out disturbing it. This beaker was then kept in a constant temperature water bath. The beaker was allowed to stand for 30 min at 45oC constant temperature.

After completion of fi lms deposition the substrates were removed from the beaker and cleaned with distilled water, then dried in air. The thickness of the obtained fi lms was about 110±10 nm.

These fi lms were subjected to an absorbed dose of γ-Rays from 137CS 1 µci for two weeks.

Transmittance and absorbance spectra were recorded in the wavelength range 360-900 nm before and after irradiation.

3. Results and discussion

Figure 1 shows the refl ectance spectra of CuS thin fi lms before and after ir-radiation as a function of wavelength. It is seen that the refl ectance is limited only by the surface refl ectance of about less than 20% in the visible region; also the values of the irradiated samples are bigger than the value of un-irradiated sample for the same wavelength. This might be due to the increase in surface roughness after irradiation.

γ-Radiation effects on some optical constants of CuS thin fi lms 595

The optical band gap Eg was determined using Tauc’s plot where the absorp-tion coeffi cient is a parabolic function of the incident photon energy hν. This relation is given by (14):

[1]

where A is a function of refractive index of material, reduced mass and speed of light.

The plot of (αhv)2 as a function of incident photon before and after irra-diation is shown in Figs. 2 and 3 respectively. It is clearly seen that the optical energy gap decreases after irradiation from 2.31 eV to 2.25 eV.

α =

A(hv −Eg )1/ 2

hv

FIG. 1

Refl ectance spectra of CuS thin fi lms before and after irradiation as a function of wavelength

FIG. 2

(αhv)2 vs photon energy for CuS thin fi lms before irradiation.

N.F. Habubi - S.S. Chiad - F.H. Ahmed - A.S. Mahdi596

The decrease in the value of optical energy gap may be due to decrease in the disorder of the crystal.

The refractive index of the fi lms was determined from the following relation (15):

[2]

where n is the refractive index, K = αλ/4π is the extinction coeffi cient and R is the refl ectance.

The refractive index values dependence on wavelength was shown in Fig. 4. As seen in this fi gure, the value of refractive index increases after irradiation in comparison with its values before irradiation, also the behavior of the graph seems to be nearly constant after irradiation. The refractive index may be a good parameter to detect the packing density: as the refractive index increases, the packing density also increases; the increase in packing density may be attributed to the structural changes due to exposure to γ-rays.

The extinction coeffi cient dependence on wavelength is shown in Fig. 5, the K value of the fi lm after irradiation became larger than its value before irradiation, the graph of K after irradiation seem to be nearly constant up to 600 nm and then suffer a slight increase after 600 nm, this is due the lattice contraction and the disorder of the fi lms.

The dielectric constant can be defi ned as:

[3]

The real ε1 and imaginary parts ε2 of dielectric constant are related to n0 and K values. These values can be calculated using the following relations (15):

FIG. 3

(αhv)2 vs photon energy for CuS thin fi lms after irradiation

n =

1+ R1−R

+4R

(1−R)2− K2

ε = ε1 + iε2

γ-Radiation effects on some optical constants of CuS thin fi lms 597

[4]

[5]

FIG. 4

Refractive index versus wavelength of CuS thin fi lms before and after irradiation as a function of wavelength.

FIG. 5

Extinction coeffi cient versus wavelength of CuS thin fi lms before and after irradiation as a function of wavelength.

ε1 = n2 − K 2

ε2 = 2nK

N.F. Habubi - S.S. Chiad - F.H. Ahmed - A.S. Mahdi598

Figures 6 and 7 present the dependence of the dielectric constant of the CuS thin fi lms on wavelength before and after irradiation. The real and imaginary parts follow the same pattern in the sense that, the values of them after irradiation are higher than its value before irradiation for a particular wavelength, and the values of real part are higher than imaginary parts.

FIG. 7

Imaginary parts versus wavelength of CuS thin fi lms before and after irradiation as a function of wavelength.

FIG. 6

Real part versus wavelength of CuS thin fi lms before and after irradiation as a function of wavelength.

Figure 8 shows the variation of the optical conductivity with wavelength before and after irradiation. The optical conductivity is determined using the rela-tion (16):

γ-Radiation effects on some optical constants of CuS thin fi lms 599

[6]

where α is the absorption coeffi cient and c is the velocity of light. The optical con-ductivity directly depends on the absorption coeffi cient and is found to increase for lower wavelength. The values of the optical conductivity after irradiation are higher than their values before irradiation for a particular wavelength.

σ =

αnc4π

FIG. 8

Optical conductivity versus wavelength of CuS thin fi lms before and after irradiation as a function of wavelength.

4. Conclusions

CuS thin fi lms were successfully deposited using chemical bath deposition.The irradiation of γ-rays affects all parameters under investigation. That oc-

curs because γ-rays increase the crystallanity disorder.

REFERENCES

(1) J. ZOU, J. ZHANG, B. ZHANG, P. ZHAO, X. XU, J. CHEN, K. HUNG, Synthesis and Charac-terization of Copper Sulfi de Nanocrystal With Three Dimensional Flower-Shape, J. Mater. Sci., 42, 9181-9186 (2007).

(2) RS. MANE, C.D. LOKHANDE, Chemical Deposition Method for Metal Chakcogenide Thin Films, Mater. Chem. Physics, 65, 1-31 (2000).

(3) M. CHEN, J. ZHAO, X. ZHAO, Scanning Electrochemical Microscopy Studies of Micro-patterned Copper Sulfi de (CuxS) Thin Films Fabricated by a Wet Chemistry Method, Electrochem. Acta, 56, 5016-5021 (2011).

N.F. Habubi - S.S. Chiad - F.H. Ahmed - A.S. Mahdi600

(4) P.K. NAIR, M.T.S. NAIR, Chemically Deposited SuS-CuxS Thin Films With High Solar Absorptance: New Approach To All-Glass Tubular Solar Collectors, J. Phys. D:Appl. Phys., 24 (1991) 83.

(5) A. GALDIKAS, A. MIRONAS, V. STRTAZDIENE, A. SETKUSA, I. ANCUTIENE, V. JANICKIS, Room-Temperature Functioning Ammonia Sensor Based on Solid State CuxS Films, Sensors Ac-tuators, B67, 76-83 (2000).

(6) Y. LU, X. MENG, G. YI, J. JIA, In situ growth of CuS thin fi lms on functionalized self-assembled mono-layers using chemical bath deposition, Journal of Colloid and Interface Science 356 (2) 726-733.

(7) C. NASCU, I. POP, V . LONESCU, E. INDRERA, I. BRATU, Spray Pyrolysis Deposition of CuS Thin Films, Mat. Lett., 32 (2-3), 73-77 (1997).

(8) L. REIJNEN, B. MEESTER, A. GOOSSENS, J. SCHOONMAN, Atomic Layer Deposition of CuxS for Solar Energy Conversion, Chem. Vapor Deposition, 9 (1), 15-20 (2003).

(9) R. BLACHNIK, A. MULER, The Formation of CuxS from the Elements: Copper used in Form of Powders, Thermochim. Acta, 361 (1-2), 31-52 (2000).

(10) A.P. GONCALES, E.B. LOPES, A. CASACA, M. DIAS, M. ALMEIDA, Growth of CuS Platelet Single Crystals by High Temperature Solution Growth Technique, J. Crystal Growth, 310, 2742-2745 (2008).

(11) L.A. ISAC, A. DUTA, A. KRIZA, I.A. ENESCA, M. MANU, The Growth of CuS Thin Films by Spray Pyroltsis, International Conference on Nano- since and Technology, J. of Physics: Con-ference series, 61(2007)477-481.

(12) Y.B. HE, A. POLITY, I. OSTERREICHER, P. PHISTERCR, R. GREGOR, B.K. MEYER, M. HARDT, Hall Effect and Surface Characterization of Cu2S and CuS Films Deposited by RF Reactive Sputtering, Physica B: Condensed Matter, 308-310, 1069-1073 (2001).

(13) P.A. ILENIKHENA, Comparative Studies of Improved Chemical Bath Deposited Copper Sulphide (CuS) and Zin Sulphide (ZnS) Thin Films at 320 K and Possible Applications, African Phys. Rev., 2, 59-67(2008).

(14) J. TAUC, A. MENETH, States in the Gap, J. of Non-Cryst. Solids, 126, 569 (1972).(15) J.N. HODGSON, Optical Absorption and Dispersion in Solids, (North-Holland Publ.

Co., London, UK, 1972).(16) J.I. PANKOVE, Optical Processes in Semiconductors, (Dover Publ. Inc, New York, 1971).

ATTI DELLA “FONDAZIONE GIORGIO RONCHI” ANNO LXVII, 2012 - N. 4

INDEX

Instrumentation A.A.D. AL-ZUKY, M.M. ABDULSTTAR, Camera Zoom-Dependent to estimate Object’s Range

History of Mathematics A. DRAGO Antonino, La geometria non euclidea come la più importante crisi nei fondamenti della matematica moderna

History of ScienceM.T. MAZZUCATO, Ignazio Porro: un geniale ma poco conosciuto ottico

LaserM.F.H. AL-KADHEMY, E.M. ABWAAN, M.A.M. HASSAN, Microstructure Be-havior of Laser Dye Fluorescein Doped PMMA Thin FilmsS.M. ARIF, B.R. MAHDI, A. ABADI, A. JABAR, S.M. ALI S.M., A Compact Syn-chronous UV-IR Laser System with Unifi ed Electronic Circuit of Blumlein Type.

MaterialsA. HASHIM, Preparation and Study of Electrical Properties of (PS- AlCl3.6H2O) CompositesA. HASHIM, Effect of Silver Carbonate on electrical properties of PS-AgCO3 com-posites

Nuclear PhysicsM.H. JASIM, Z.A. DAKHIL, R.S. AHMED, The internal transition rates of pre-equilibrium nuclear reactions in 232Th

OphthalmologyM.F. ABBAS, The effect of hyperthyroidism on visual acuity and refractive errors

Solar PanelsN.K. KASIM, A.J. AL-WATTAE, K.K. ABBAS, A.F. ATWAN, Evaluating the per-formance of fi xed solar panels relative to the tracking Solar Panels under natural de-position of dust

Strip LinesA.A. AZEEZ BARZINJY, Theoretical analysis of normal and superconducting strip-line parameters

Thin Films N.F. HABUBI, S.S. CHIAD, F.H. AHMED, A.S. MAHDI, Gamma-Radiation Ef-fects on Some Optical Constants of CuS Thin Films

VarietyC.M. ROSITANI, L’uomo Vasco Ronchi

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