Franco, Judas

Patel, N K

Pathak, P D

IACS Institutional Repository

Indian J. Phya, 49, 368-372 (1975)X-ray study o f photosensitive film on copper in aqueous solution o f ferric chlorideJ fdas Franco, N, K. Patel and P. D. Pathak*Chern/iMry Department. Bhavan's R. A . College of Science. Khanpur^ Ahtmdabad-X,Qujrat(Received 12 November 1974)PhotoHoasitivo film iB formed on electrolytic copper plate by treat­m ent w ith aquoouB solution of ferric chloride. The film is found  to  bti of CuCl, by X -ray analysis. I t  is phototropic and photosensi­tive  in nature. I t  gives photoprint and produces photocurrent when  exposed to  sunlight. The photocurrent increases to  a m axim um  when the film is exposed in dry condition to  sunlight; but if  the film  is exposed to  sunlight after m oistening with water, the photocurrent increases to  m axim um  and then decreases and then becomes constant in about three m inutes. The mechanism of change in polarity o f  the photocurrent is explained. The X -ray diffraction study o f the  film obtained shows the form ation o f (CugO) cuprous oxide, as one of the products o f primary photochem ical reaction.1. IntroductionFerric chloride is an excellent etching agent for copper and has been extensively  used in the preparation of printed circuits (Nekervis 1962, Saubostre 1959,* Sharpe & Garn 1959). The product o f action o f ferric chloride on copper is CuCl whicli is insoluble in water and forms an adherent layer on the copper plate surFaoo. Solid CuCl immersed in water exhibits photochrom ic properties as reported by number of workers (H echt & Miller 1954, W ojtczafi 1957, Singh 1922). But the ifiiotochromic property of CuCl as a pure product has been studied  by these workers. The action o f light on CuCl film on copper plate in presence o f moisture has not been reported. Thin films have properties different from pure products. The base copper metal surface as well as photoadsorption oi‘ oxygen has catalytic effect on photochem ical reaction w ith CuCl. In  the present work the product o f photochem ical reaction w ith CuCl in presence o f moisture and oxygon has been studied by X -ray  diffraction study o f th e film in contact with the copper plate. The stu d y shows th at the primary photo chehiical reac­tions produces (Cu-^O) cuprous oxide. Secondary products have not been investi­gated. The formation o f CugO is also supported by the study o f reversal ol photocurrent when CuCl film is exposed to  light m oistened w ith  water.Physios Department, University School of Soienoes, Gujrat University, Ahjnedabad-6*368on copper 3692. EXFBRlMEin?ALA coppor specim en o f 99.8%  Cu was used. Cleaned and polished accprrding \if (ho m ethod suggested b y  Champion (1952). The cleaned copper was immersed  hi O.lM  aqueous ferric chloride solution for 10 m inutes at room temperatures. 1 ’hcn it was washed w ith  distilled  water and dried. This operation was carried out in the dark. The film on half th e surface o f th e  plate was scraped out com- plcttoly. The film on th e back side o f  the plate was also scraped out. The film surfiioo and the coppor surface were connected to  a sensitive ballistic galvanom eter l)V silver paint contact and exposed to  sunlight in dry condition and the photo- onrrent was measured w ith tim e o f exposure. The experim ent was repeated  l>y measuring the photocurrent after m oistening th e film w ith distilled water. Foi' X-ray diffraction study the film was prepared chem ically on the copper as de^scribod above and th e film in contact w ith  copper plate was used for X-i*a.y diffraction study. The X -ray equipm ent used was a o f Philips Inc. ffolland type P W  1009 w ith extra stabilizer unit. A  800 w att water cooled Philips tube having a copper target was used as the X -ray tube. The X -ray  iK^ am was passed through a nickel filter to  cut o ff the /^-component. It emerged at an angle o f to  th e normal to  the tube window. The copper plate having  llin film on its surface was put at the centre o f  tlie horizontal diffractom eter disc. TIio disc was calibrated in degree (0), each degree divided into four pai-ts and iiad a. diameter o f 500 mm. The Geiger counter was enclosed in a cylindrical emdoHure with a slit in front o f it, and the counter could be rotated on the gra­duated scale about th e specimen. The specim en was flat having an area o f  () X   ^sq. cm. and rotated a t h a lf the speed at which th e Geiger counter wasroratod, so that its surface rem ained tangential to  th e focussing circle. The Geiger counter was rotated by a  synchronous m otor at th e speed o f h a lf a jpinute per degree. A s(!reening i)late w ith a slit o f about 3 m m  was placed in front o f the counter to cut off stray radiation. The pulse o f th e Geiger counter was fed to  a rate- through an am plifying circuit. A  micrometer put in the ratem eter showed  a diffraction whenever a Geiger counter passed across an X -ray line. Thus the position o f th e X -ray lino could be located and read on th e diffraction scale. Tbc scale of the m icroammeter was d irectly calibrated in colints per second, and  c o u ld  bo read upto m axim um  30,000 per second. The recorder was run 1200 niui per m inute. The wave length o f X -ray used was 1.5405 A .U , The X -ray  diifraction spectrum  o f th e film was taken.N ext a polished copper plate 6 x 3 sq.cm , was m ounted on th e diffractom eter disc and X -ray diffraction spectrum  for copper was recorded.Finally cuprous oxide (B .D .H . quality) was pressed on  a glass slide. This was m ounted on th e diffractom eter disc and the X -ray diffraction spectrum for ^^ tiprous oxide was recorded,370 J. Franco, N- K. Patel and P. D. Pathak3. DiboitssionFerric chloride reacts w ith  copper giving CuCl w hich rem ains adherent oniho pjate.2FeCl3+Cii CuCl2+2FeClo C u C l2 + C iw 2 C iiC l.P om baix (1967) caRsociatod a deprossion o f potential o f copper brought about by illum ination with th e presence o f cuprous chloride on its surface. Lucey(1967) indicated that illum ination o f copper produced a more negative potential i f  the m etal was covered by cuprous chloride film and a more positive potential when it was covered by a cuprous oxide film. T hey have utilized  these observa­tions to  explain p itting corrosion o f copper pipes. CuCl is photosensitive and when sunlight falls on it produces a photocurrent which changes its polarity with  tim e (Francoo & Patel 1973). Tt is also photosensitive and gives a x>hotoprint. W hen sunlight falls on CuCl film formed on copper exposed in dry condition, the photoourront increases to m axim um  but on m oistening th e film with distilled  water the photo current increases to  m axim um  and then  decreases or reverses and then  in about three m inutes becom es constant. The reversal if  photo­current has been attributed to  photosolvation followed by photooxidation  duo to  i)rosence o f photoadsorbed oxygen. CuCl is an n typ e sem iconductor. It is photosensitive and produces xfiiotocurrenthvCuCl+^^HoO----- > CuCl................. HgO(com plex)CuCl.............H 2O + O 2 ->  C1I2O + H C I+ o th e r  products(complex) photoadsorbedCU2O is formed as a result o f photoroaction given above. As C112O is a p- typo sem iconductor, th e presence o f CuCl and CugO forms an semiconductoi* junction which explains the leveling o f photocurrent in  three m inutes. The formation o f CuaO was proved by X -ray diffraction study. The X -ray diffrac­tion study of the film shows peaks for CugO, Cu and CuCl. A ll have cubic lattice. The values for a for Cu, CugO and CuCl lattice are 3.608 A .U ., 4.26 A .U . and 5.407 A.U. respoctiv(^]y (Hodgm an et al 1959). The diffraction angle (0) for peaks Avere theoretically calculated for different h, k, I values using th e equationA_2 sin 6and these values Avere compared w ith  those obtained in the X -ray  diffraction  spectrum. Figure 1 is the X -ray diffraction spectrum  for th e film obtained on copper plate, I t  shows peaks for cuprous-chloride a t diffraction angles 14°17',P h o to se n s itiv e  f i lm  on c o p p t t d l l2;V'45' and 28°ir and also peaks for cuprous oxide (CuaO) at diffraction angles IS 15' and 30*^ 45' and peaks for copper (due to  th e copper base below th e film) diffraction angle 21®4r and 37°8', figures 2 and 3 are X -ray diffractiofi spec- Inims for copper and (CugO) cuprous oxide taken  to confirm the peaks obtained  fni Cu and CugO in figure 1 for th e film product.h'lu,. 1. X-ray diffraeiion spociruiri of CiiCl film on copper plate, al’toj* exposure to sunlight m pj osonce of moisture.6(h £ soK§ H| 3 0 -§ 20-Xg  lO- 0T— I— r12 16 20 24 20 32 3 6  4 0  44  46ANGLE OF DIFFRATIONFig. 2. X-ray diffraction spectrum of copper.Fig. 3. X-ray diffraction Bpoctmm of cuproud oxide.372 J. T^ ranco, N, K, tatel and P. D. Pathak4. Co nclusio nsThe formation of pliotopriut on the CuCl film obtained on copper m ay be due to photochemical reactions between CuCI, water and photoadsorbed oxygen  in pj'(^sence of sunlight. The primary photochem ical reaction gives rise to  form a­tion of cuprous oxide (CugO). The photo current increases to  m axim um , reverses and then levels o ff within three m inutes. This levelling o f photocurrent m ay be duo to presence o f CuCl an 9^ -type sem iconductor and CugO a ^  typo sem iconductor forming n-p- junction. The X -ray diffraction study confiim s the form ation of cuprous oxide (CugO).R e f e r e n c e sChampion F. A. 1962 {Jorro&ion Testing Processes, Chapman and Hall London, p. 187.Franco J. & Patel N. K. 1973 British Corrosion Journal 8, 236.Hooht H. & MilJer 1954 Z. Physik. Chem, Leipzig. 202, 403.Hodgman C. D., Woast li .  C. & Selby S. M. 1969 Hand Booh of CImnistry and Physics, (40tliedition) Chemical Rubber Publiccation, 2687. Loeoy V. F. 190'7 British Corrision Journal 2, 176.Nokervis W. F. 1962 The Use of Ferric Chloride in the Ftching of Copper, Dow Chemical Co.Midland, Mich.Pourbaix M., Van Muylder J. Van Lear P. 1967 Corrosion iSciencG 7, 795.SaubegO-e jfl. B. 1969 Ind. Eng, Chem. 51, 28H.Sharpe L. H. & Gam P. D. 1959 Ind. Eng. Chem. 51, 293.Singh G. 1922 J. Chem. Hoc. 121, 782.Wojtczak J. 1967 Zcszyty Nank. Univ. Posnan. Mat. Chejn. 1, 26.

X-ray Study of Photosensitive Film on Copper in Aqueous Solution of Ferric Chloride

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X-ray Study of Photosensitive Film on Copper in Aqueous Solution of Ferric Chloride

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