././Viw. 78 (7), 599-605 (2004)
/ \
U P ^
Cheinic^^ analysis techniques for quantitative determination of Cd, Se and Te from thin CdSe^^Te^ films
P D More*, P N Bhosalc-, A A Belhekar^ M K Dongare^ and L P Deshmukh' *
‘Thm Film and Solar Studies Research Laboratory, Department of Pfiysics (AppI Elect ). Shivaji Umvcrsit) ( Vnlei for V (i Studies.
Solapur-Pune Road, Kegaon, Solaftur-4n 002. Mahanishua. India
^Materials Research Laboratory. I^epariricnt ol Chemistry. Shivaji University.
Kolhapur-416 004, Maharashtra, India
^National Chemical Laboratory, P«ne-4II 008, Mahaiashtia. India E-mail • morc_piavift((ZOcdiffmail com
R e ( e i v v ( i 2 ^ J i i n u a n 2 0 0 3 , a c v e p t e d J 8 M a \' 2 0 0 4
\bstract A method is proposed for the chemical ctunpositional analysts of the mixed scmicondutiing thin films Fhe lcchnic|uc is picsenily used
01 cuiactum, sepaiaiion and spectrophoiomclnc determination of cadmium (H), selenium (IV) and telluiium (IV) fiom sulphuric acid and hydixKhlonc ilkI mcciM with 4’-bromo PTI*T in chloroform This method is sensitive, rapid, reproducible and has been satisfactorily applied loi the sepuiaticm and ktcnmnaiion ot trace amounts ot Cd, Sc and Tc from ('dSc,^Tc^ thin films The results are compared with analysis of these films by an EDS technique
\i*\words ('hemical analysis, semiconducting thin lilms, PAR leagcnt, 4' bromo PTIH' l‘\('S No. 68 5 5 .Nq
I. Introduction
The increasing awarene.ss o f todays scientific technology to
^(ud\ the materials properties that are best suited for a variety '! clivii ical and electronic devices, led to the necessity for their
^iianiiiative m easurem ents at trace and ultra trace levels,
^loienver, the preparation o f highly pure and special class Tiateiials for use in microelectronics, energy generation devices, iiiJcai energy generation and solar energy conversion, has n.Teased the demand for fast and sensitive detectit>n by the inalvtical techniques, since even a trace amount of metal ions
> divert stoichiometry and affect the properties of such materials considerably. Among the various analytical methods,
‘Patrophotomeiric technique has a prominent place in view of Jbgh .selectivity and sensitivity, reasonable cost of the
^It^^pments and freedom from mutual inter-elemental interference.
large number of materials like II-V I, IV -V I, III-V, I-JII-V compounds have been analyzed by a variety of techniques methods, electroanalytical and spectroscopic AAS, EDS, XPS, SIMS etc) [ 11- In general, extraction are considered more useful and are preferred. The steps not only enhance the selectivity of a method
^ Author
but also provide its enrichment of the determination. A basic spectrophotometric method is simplest, convenient and employs a relationship between the absorption of the radiation by a solution and the solution concentration (1,21. The analysis of cadm ium , selenium and tellurium from sem iconducting CdSe, Te^ m solution state was therefore, carried out using a spcctrophotmnctnc technique. The method gives an average of the constituents of the films as the sample preparation was m the solution .state and was prepared from uniformly deposited thin films.
2. Methods and m easurem ent details 2. / Materials synthesis :
CdvSe, CdTe and CdSc, Te^thin film samples with 0 < a < J were synthesized on the optically plane glass substrates by a chemical deposition process reported elsewhere [3,4|. Toobtain thin layers of the above samples, equimolar solutions of cadmium sulphate, sodium .selenosulphitc and sodium tellurosulphitc were allowed to react in a stoichiometric proportion to vary v from 0 to 1.
Triethanolamine wa.s used as a complexing agent and pH of the reaction mixture was maintained at 10.4 ±0.1. The well-cleaned glass plates were rotated with a constant speed in the reaction
© 20041ACS
600
gravimetrically by reducing with hydrazine sulphate
P D More, P N Bhosale, A A Belliekar, M K Dongare and L P Deshmukh
m ixture by em ploying a substrate holder. This provides a provision for constant automatic mechanical churning of the reaction solution during deposition. Good quality deposits, are obtained at 70 ± 2“C deposiii()n temperature, 90 min deposition time and 72 ± 2 rev. min ' as speed of the rotation.
2.2 Preparation o f the semiconductor solution :
The semiconductor thin films dept)sitcd as above were first dissolved in a dilute HCI and evaporated to moist dryness and then diluted to 50 ml with distilled water. The resulting sem iconductor solution contains cadmium (Cd^^), selenium (Se^“) and tellurium (Tc^’) ionic species o f Cd, vSe and Te respectively f2,5,61.
2.3 Standardization o f cadmium (fl), selenium (IV) and tellurium ( IV ):
(a) Cadmium (I!)
A. R. grade 0.5705 gm cadmium sulphate was dissolved in a minimum quantity of distilled watci and 2 ml concentrated H,SO^
was added to it. The solution was then diluted to 250 ml with distilled water [5J, [concentration of Cd“' Img/ml].
Then 10 ml, 20 ml, 40 ml, 60 ml, and 80 ml standard solution of Cd^*^ were taken in the 1 tX) ml measuring flasks and 5 ml 0.01 % PAR reagent and 10 ml 40V<> ammonium acetate were added to each of the flasks and diluted to 100 ml with distilled water. Four ml semiconductor solution containing Cd'^ ions in a 100 ml measuring flask was pipetted out and 5 ml 0.01% PAR and 10 ml 40-% ammonium acetate were added to it and diluted to 100 ml w ith d istilled water. T his solution consists o f unknow n concentration of Cd*"^ in a sem iconductor sample. Optical absorbance of this solution was m easured for each of the solution in the range of wavelengths from 400 nm to 750 nm.
From the absorbance measurements, was determined and it was 510 nm. Plotting the graphs o f absorbance vs concentration o f Cd‘^^ Beer's ranges as well as concentration of Cd'*^ in a semiconductor solution were determined.
(h) Selenium (IV)
Selenium (IV) was prepared by dissolving 1.756 g selenium dioxide, alkali selenite [F-Merck] in cone. H C 1, diluted to 250 ml distilled water and standardized with SO, method [2,6]. Then 10 ml, 20 ml, 40 ml, 60 ml and 80 ml standard solution of Se’~ were taken in 100 ml measuring flasks and 10 ml 0.02M, 4'-brom o PTPT reagent in chloroform was added to it. After allowing two phasCvS to separate, the organic phase was collected in a 10 ml standard flask and made upto the standard mark. The absorbance w as determ ined at 350 nm w avelength and is shown in Figure (a).
(c) Tellurium (IV)
1.785 g of stxlium trioxotelluarate I Na^ TcO^ BH^Ol was dissolved in distilled water, diluted to 500 ml and standardized [7]
stock solution was diluted to obtain a working .solution on concentration with distilled water. The remaining procedui same as above (selenium IV). The absorbance wa^
at 440 nm wavelength and is shown in Figure 1(b).
Figure 1(a). AbNorbance curves of Sc (IV) 4’-bronK) FTP I loi 20 ppm, 11-30 ppm, 111-40 ppm and IV-50 p])m|
Figure 1(b). Ab.sorbance curves of Tc (IV) 4’-bromo PTPT umipkx 2 ppm, II-4 ppm. IIF6 ppm and IV 8 ppmj.
2,4 Preparation and properties o f4 '‘hronio PTPT:
4 ’-bromo PTPT was synthesized in two steps using method [2,81- In first step, 2- methyl - 2-isothiocyanato - pentanone was prepared while in the second step, the produd was condensed with p-bromoanilinc in the presence ol | acid to obtain 4'-bromo PTPT.
49.0 gm (0.5M) sulphuric acid dissolved in 50 ml watet v added over a period of 15 minute to 98 gm ( IM) mesityl oxA 15"C. 76 gm (IM ) ammonium thiocyanate dissolved m distilled water was added quite rapidly to the above room temperature. After shaking for over 15 minutes, tlieupP<^^
Chemical analysis techniques for quantitative determination of Cd. Se and Te
etc 6 0 1 ,ilv layer was separated and washed with distilled waterJ '^J„l free from acid. The final residue was then dried by keeping : ‘“’Jiji, anhydrous .sodium sulphate for overnight. The yield of I pioduci 2 - methyl - 2- isothiocyanato - 4-pentanone was
; i.o'f? with respect to the mesityl oxide [2,9].
lo synthesize 4'-bromo PTPT, 2-methyI-2-isothiocyanato - ' 4pi'nianonc was mixed with 4'-bromoaniIine 1.3.44 gm, (0.02 M) li,solved in .SO ml ethanol). Then, 15-25 drops of concentrated II so vveie added to the reaction mixture and reaction mixture wa.s refluxed for 2 0 -2 5 minutes and ccxilcd at nx>m temperature.
4ciyMalhne product so obtained was precipitated out which nasieeiysiallised with an A. R. glacial acetic acid, washed with jistilled water and air-dried. The product was colourless, fine
•ivsialhnc .shining solid with a sharp m.p. at 188 ± 1"C. The molecular lormula of the resultant compound is C|,H|^N,SBr and its molecular weight is 311. Its practical yield, on the basis nip bromo aniline taken, was 53% [2,10]. The compound is Miliihle and .stable in chloroform, N-N-dimethyl formamidc, DM.SO and 1,4 dioxame and insoluble in water and sparingly soluble in ethanol, acetone and methyl isobutyl ketone. A profile proposed fo i .synthesis of 4' bromo F fP T is given below
n i, I
H C ( =C-( ’- n i , + H,SO,-r NH..SCN\ I A 4 II
0 Mcsitvl oxide
(-H,
I
I
II 0 S-C = N CH,
I
II
o
8-C’ = is|
0.5 mole H,SO^ in 50 ml 1120 + IM mesityl oxide at 150C+ 100ml ammonium thiocyanate; solution stirred and upper oily layer separated.
(2 ~ methyl 2~isolhiocyanato 4- pentanone)
N R
(p-bromoaniline)
^ 02M 2 - methyl 2-isothiocyanato 4 - pentanone + 0.02 p - 50 ml + 15-20 drops HjSO^. Refluxed for 15-20
Br
The absorption spectrum of 4'- bromo PTP1’ in chloroform is shown in Figure 2. The absorbance shows that the reagent Exhibits a sharp absorption maxima at 280 nm with the molar extinction coefficient of 9.55 x lOVinoF* cm"*.
10
0 8
0 6
X 0 4
0 2
/ *
\
250 30 0
W a v e le n g th , nm
350
Figure 2. UV - visible sjicclia 4'-bmmo PTPT in chloroform 2.5 Extraction, separation and analysis o f C\E\ 5V-' and Te~
from the semiconductor solution :
A 25 ml semiconducting solution was taken and 10 ml, 5.5M I ICl was added to it. The mixture was shaken well and transfurred to a 25 ml separating funnel. 10 ml, 0.08 M. 4'-bromo PTPT in chloroform was added to it and is shaken for 4 min. The proposed separation scheme is shown below :
Flow Chart
CD (II), Se (IV) and TE (IV) solution I---^--- 1 An organic layer containing
yellow coloured solution.
An aqueous layer containing CD^“^ .solution Selenium (IV) and tellurium (IV) evaporate
An organic layer containing Se(IV) and absorbance
measured at
X = 350 nm
^ mux
An aqueous layer containing Te(IV) and absorbance
measured at
^ =440nm
^ max
An aqueous layer (CM^^) solution evaporated to dryness and diluted to 25 ml with distilled w ater + 4 ml semiconducting solution + 5 ml 0.01 % PAR + 10 ml 40%
ammonium acetate and diluted to 100 ml with distilled water.
6 ()2
P D More, P N Bhosale, A A Belhekar, M K Dongare and L P Deshmukh
25 ml semiconductor solution containing Cd“^ Sc“" and Te“~was extracted in the 10 ml, 5.5 M I ICl and 10 ml, 0.08 M 4-bromo PTPT in chloroform. The time required for formation of Se and Te - 4' - bromo PTPT complex was 4 min. After shaking, the Se and Te ions form yellowish coloured complexes with 4‘-bromo PTPT and achieve an organic phase, while Cd-'^ remained in an aqueous phase. The organic phase containing Sc and Te ions were evaporated to moist dryness and diluted with 25 ml, 3.5 M HCl and extracted with 4'-bromo PITT. Now, the aqueous solution contains Se (IV) and organic layer contains Tc (IV).
The absorbance of aqueous solution containing yellow coloured complex of Se (IV) 4''-bromo PITT was measured at 350 nm w avelength against chloroform as a blank by UV spectrophotometer. The organic phase consists of yellow coloured complex of Te (IV) 4’-bromo PITT and the absorbance of solution was measured at 440 nm wavelength.
The Cd^‘*“ which was separated in the first step was analyzed using PAR 4-(-2- Pyridylazo) - resorcinol (II). In the actual analysis, 5 ml, 0.01 % PAR solution was added in an aqueous phase containing cadmium in which 10 ml 40% ammonium acetate solution was added. The solution was then diluted to 50 ml with distilled water. The solution acquires orange colour, the optical absorbance of which was measured at 510 nm wavelength using reagent blank solution as a reference.
3. Results and discussion
3.1 The spectrophotometric analysis of Cd, Se and Te from the solution state :
(a) Analysis of Cd-"^
4’-bromo PITT forms a strong and highly stable complex with selenium and tellurium at varying concentration of the hydrochloric acid. It was observed that chloro complexes of these elements react at different rates with 4'-bromo PTPT’ and imparts intense colours to metal complexes. Therefore, it becomes very easy to separate selenium (IV) from the tellurium (IV) present in the mixed chalcogenide thin films. After separation o f the species, analysis was carried out using a spectrophotometric method. The concentrations of cadmium, selenium and tellurium can effectively be determined using the PAR and 4'-bromo PTPr complexing agents. From the results, it is revealed that cadmium content present in the film and in the deposition bath fairly matched with the amount that was actually taken for the deposition. Initially, a total of 5620 ppm cadmium was taken for deposition of the film and out of this 2849 ppm get deposited as a film whereas 2759 ppm were detected in the residue. Total cadmium content found in the film and in the bath was slightly less than the amount taken initially for deposition.
This may be due to the errors caused in the dilution, preparation of the solution and in the measurements too. Table 1 gives the results obtained by this technique. It appears that the film
content + bath residue content is approximately equii
content taken for deposition. In
Table 1. Spectrophotometric determination of Cd in Cd r
films ' '
St Sample C'omp- Amount Amount Amount Aniount" ' No No. osition ofCd of Cd of Cd ol (\| (,
X found in found in found in taken K>r | film, bath, film+ deposition ppm ppm btnth. ppm ppm
1 p, 0 2849 2759 5608 5620
2 p. 0 0 2 2823 2788 561 1 5620
3 p, 0 04 2828 2791 5619 5620 ■^(1 ,
4 p. 0.06 2825 2789 5613 5620 Sn V
5 p. 0 08 2821 2791 5612 562(f X!) j
6 p. 0 . 1 2831 2780 5611 5620 5 ( 1 ’
7 p, 0.15 2821 2786 5607 5620 ^(1
8 p. 0 2 2812 2800 5612 5620 M' 1)
9 p. 0 3 281 1 2798 5609 5620 M l l;
1 0 p,„ 0 5 2816 2783 5599 5620 Xil
1 I p„ 0 7 2814 2794 5608 5620 Sm I)
1 2 p„ 0 8 2827 2781 5608 5620 M M
13 p,. 0 9 2840 2769 5609 5620 Ml '
14 p,. 0 95 2833 2768 5601 5620 M, 4.
15 p,. 1 2843 2766 5609 5620 V '
(b) Simultaneous determinaticm of selenium (IV) and tcHtiini'r.
(IV)
An yellow coloured selenium (IV)-4'-bromoPTI^ complex extracted in chloroform and it exhibited an absorptuni maximun at 350 nm. The maximum absorbance was in the concentration range from 5-6 M HCl. It was observed tliai tiu absorbance remained constant when the shaking period wa*-' minutes or more. For full colour development, 8 ml 0,02 M was used. It was found that absorbance of the complex maximum in chloroform. Under the optimum expciimcno' conditions. Beer's law obeyed over the concentration range lion 50 to 700 pg of selenium (IV) per 10 ml of the organic phase molar absorptivity was calculated to be 1.1 x 10^ 1 m o l'' cm ‘ ^ 350 nm. The complex was stable for more than 48 houi s.
In a diverse ions study, most of the cations do not interleri in the determination of selenium (IV) except for Cu (11). ( f and Bi (III). The interference due to Cu (II) and Cr (HD overcome by masking with 2.5 ml 10% tartaric acid whereax Bi (III)interference was eliminated using 3 ml 10% c itric ac ida^ i masking agent. However, tellurium (IV) inte rferes determination of Sc (IV) by this process. The optimum conditi^’J’' for the extraction of the selenium (IV) and tellurium similar. Under similar optimal conditions, both the Se (IV) (IV) are extracted with 4'*bromo PTPT Hence in order to dctcmn>^^
Chemical analysis techniques for quantitative determination of Cd, Se and Te etc
6 0 3 lelluriiim (IV) m the presence of selenium (IV), we have developedipiix ess that determines these metal ions simultaneously taking advantage of the difference in the wavelengths of the maximum jPsorbance as shown in Figure 3. The method can be applied ihe determination o f trace amounts of the tellurium (IV) and .elcnrnm (IV) in sclenotelluric acid [2]. Tables 2 and 3 give the i^.sults obtained by this technique.
Tabic 3. Speciropholomelnc tlcicrminalion of Tc in C'd (Sc. Tc) thin films
Figure .V Absorbance curves of 4'-bromo J^PT complex of ! Tellununi il\) ppm , II ' Selenium (IV), 30 ppm ; Ilf • Tellurium (IV), 3 ppm + Sckimini (IV). 30 ppm
I lom the above discussion, it appears that the analysis ol .halcogenides sem iconductors, particularly selcnides and lablc 2. Spcclrophotomctiic determination of Se in Cd (Se, Tc) thin
llllTls
''I Sample Comp- No osilion
Amount Amount Amount Amount % of of Se of Se of Sc of Sc Se in found in found in found in taken for film
film, bath, film-F deposition
ppm ppm bath, ppm ppm
I p. 0 1947 1997 3944 3948 49 31
2 p. 0 0 2 1827 2115 3942 3948 46 77
p, 0 04 1667 2267 3944 3948 42 22
4 p. 0.06 1521 2420 3941 3948 38 52
p, 0.08 1401 2530 3931 3948 38 48
6 p. 0 . 1 1268 2668 3936 3948 31 12
7 p, 0.15 1225 2713 3938 3948 31.10
H p» 0 . 2 1 187 2748 3935 3948 30 06
‘) p. 0.3 1 105 2837 3942 3948 27.97
K) P,o 0.5 1045 2891 3936 3948 26 47
11 p„ 0.7 779 3165 3944 3948 20.70
1?
p . 0 . 8 634 3319 3943 3948 16.10
13 p„ 0.9 389 3549 3938 3948 9 08
14 p,14 0.95 150 3790 3941 3948 3 80
15 P 1
_ 15 1
Sr No
Sample No
('om p' nsition V
Amount of Te found in
film, ppm
Amount ol Te found in
bath, ppm
Amount ol Te lound in
llllTH- bath, ppm
Amount %of of 7c Tc in taken lor film deposition
ppm
1 p, 0 - - - -
2 p, 0 0 2 192 6180 6372 6380 3 00
3 p, 0 04 476 5893 6309 6380 7 46
4 p. 0 06 716 5659 6375 6380 1 1 2 1
5 Ps 0 08 907 5470 6377 6380 14 32
6 p. 0 1 1 I 16 5260 6370 6380 17.50
' 7 p, 0 1.3 1 167 52 19 6376 0380 18 70
8 p. 0 2 1206 5169 6375 6380 19.90
9 p . 0 3 1404 4972 6376 6380 2 2 0 0
1 0 p,„ 0 5 1493 4881 6374 6380 23 41
V p„ 0 7 1864 4502 6366 6380 29 22
1 2 p,. 0 8 2144 4229 6372 6380 33 60
13 p „ 0 9 2576 3794 6370 6380 40 38
14 p„ 0 95 2921 3439 6360 6380 45 78
15 p „ 1 315 1 3221 6372 6380 49 40
icllu n d es, is a function o f several such factors as acid concentration, quantity of 4' bromo PTP1\ optimum absorption wavelength, validity of Beers range, concentration of PAR reagent, shaking time etc. Extraction of cadmium was can ied out over the acid concentration range from 0.1 to 0.7 M hydrochloric acid. The results indicated that the extraction of Cd in the presence of Se^" and Te^' is optimum in the Beers range from 10 to 70 ppm. The extraction of selenium and tellurium was therefore carried out over the acid concentration range from 1 to 10 M hydrochloric acid. The results showed that the quantitative extraction of Se and Te are optimum in the acid concentration ranges from 5 to 7 M and 7 to 8 M, respectively.
For cadmium amount equal to 0.01%, 5 ml PAR reagent was taken for the analysis. The effect of concentration of the PAR reagent was studied in the concentration range from 0.001 to 1 %. It is seen that a stable complex formation look place at 0.01
% PAR reagent. Therefore, an optimum concentration of the PAR reagent was selected as 0.01%.
Various amounts of 0.08 M- 4’-bromo PTPTand 0.02 M 4 - bromo PTPT in chloroform were used for 4 0 ppm selenium at 5.5 M HCl and 10 ppm tellurium at 3.5 M HCI, respectively. The absorbance remained constant when 7.5 ml, 0.02 M and 0.08 M- 4 -bromo PTFF .solutions were taken. Therefore, 10 ml 4'-bromo n 'P T .solutions were prepared for extraction and separation of Se and Te, The complete extraction of selenium, tellurium and cadmium in chloroform was ensured.
604
P D More, P N Bhosale, A A Belhekar, M K Dongare and L P Deshmukh
The colour of the selenium / tellurium 4'-bromo PTPT complexwas developed instantly and the intensity remained constant for a period of more than 48 hours.
3,2 An EDS analysis o f the Cd, Se and Te from the thin solid film state:
CdSCj^^^Te^ films were also analysed by an energy dispersive spectroscopy (EDS) technique. The contents of Cd, Se and Te are shown in Table 4. Prom the table, it is clear that the samples are Cd~ rich and compared to Te content. Sc content is slightly greater, due to the reactivity. It is also revealed that Cd““^ content in the film shows higher values than those expected for theoretical stoichiometric ratio. This can be attributed to the Hible 4. Analysis of Cd. Se and Te by an energy dispersive spectroscopy technique
Sr No.
Sample No.
Composilion
X
(d observed in film %
.St‘
observed m film %
Tc observed in film %
1 p, 0 61 41 38.59
2 p. 0 0 2 62 59 34.76 2 65
3 p, 0.04 64 58 31 50 3 92
4 p. 0.06 64 96 27 22 7.78
5 p, 0 08 65 84 2 1 0 2 13 14
6 p. 0 1 63 78 18.83 17 38
7 p, 0 15 64 97 16 95 18.07
8 p. 0 . 2 6 8 13 1 0 62 21 25
9 p. 0 3 62 85 1 0 48 26.67
10 P,o 0 5 64 34 6.48 29 18
1 1 p „ 0 8 63 8 8 3 94 32 18
12 p „ 0 9 62,54 3.18 34 28
13 p» 0.95 61.75 2.44 35.81
14 1 63.71 36.29
fact that the solubility product o f CdSe iis lower than CdTe. It
Table 5. Statistical asse.ssment of Spectrophotometcric technique
the results ubtaiiicu
Sample No.
Composition % Error of Cd
% Error
of Se ol Hirorh
p, 0 0 . 2 1 0 . 1 0
p , 0 . 0 2 0.16 0.15 0 12
p . 0.04 0 0 1 0 1 0 0 17
p . 0 06 0 1 2 0 17 0 UK
p . 0.08 0 14 0.43 0 1)7
p . 0 . 1 0 16 0 30 0 U,
p . 0.15 0 23 0 25 0 Of)
p , 0 2 0.14 0.32 0 OK
p . 0.3 0.19 0.15 0 0(,
p.., 0.5 0 37 0.30 0 00
p „ 0.7 0 . 2 1 O.IO 0 22
P n 0 . 8 0 2 1 0 1 2 0 17
Pm 0.9 0 19 0.25 0 If)
H,, 0 95 0.33 0 17 0 1 1
1 0 19 0 1 ^
means that CdTe is more soluble in the reacting solution and whatever excess Cd^*^ content observed may be due to the deposition of Cd^"*^ - OH” on the substrate during growth process [11]. Theoretically, it is also expected that during crystallization o f CdSe and CdTe in hexagonal and tetrahedral structures due to the small size of Cd“*^ (0.95 A^), more and more Cd^'^ ions get packed in a unit cell of CdSe / CdTe. The statistical assessment o f the results obtained by the spectrophotometric analysis technique (Table 5) shows a little difference between the results because EDS gives spot analysis 112] of Cd^"^, Se^“ and Tc^”
w hile sp ec tro p h o to m e tric tech n iq u e show s an average composition of Cd^'^. Se^“ and Te^" in CdSe,^^Te^ thin films [2,51.
4. Conclusions
We have applied the spectrophotometric analysis technique I m
the first time for the chalcogemde .semiconducting thin tilm^
One of the important features of the method described is (ha! 't offers a very .sensitive and selective separation of Cd(ID fn-in Se (IV) and Te(IV) compared to other methods ol analysis hkr EPMA, XPS, AAS, etc. Our method is economical, very convenient, reproducible and rapid. The EDS resiilt.s revo.ilai that the Cd^"*" content in the film is higher than those expccial for theoretical stoichiometric ratio. The variation in pcrceniagi' error of an EDS analysis can be explained on the basis ol ilu‘
non-stoichiometry of CdSCj^^Te^ thin films. The relative stand.nJ deviations listed in Table 5 for spectrophotometric analysis ot Cd (Se, Te) thin films show that a slight variation in perccniaic of Se^” and Te^~ may be due to the dilution factor and an instrumental error. In brief, the spectrophotometric lechniqat is an excellent alternative to analyse the semicondiKtoi materials.
R eferences
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(2002)
[4] P D More, G S Shahane, L P Deshmukh and P N Bhosale C lien t, P h y s . (In Pres.s)
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