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Effect of deposition time on structural, electrical, and optical
properties of SnS thin films deposited by chemical bath deposition
Applied Surface Science 257 (2010) 1189–1195
E. Guneri, C. Ulutas, F. Kirmizigul, G. Altindemir, F. Gode, C. Gumus
Advisor：王聖璋 副教授
Advisee：黃俊嘉
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Outline
 Introduction
 Experimental
 Results and discussion
 Conclusions
 Future works
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Introduction
 Recently, a variety of binary semiconductors especially from the IV–VI groups of
periodic table have been studied due to their small energy gap and potential use in
solar cells. SnS is one of them.
 It’s direct and indirect band gap values in orthorhombic crystalline structure are
between 1.3–1.5 eV and 1.0–1.1 eV , respectively.
 It displays a higher absorption coefficient (∼105 cm−1) than other materials such as
GaAs and CdTe. It has p-type conductivity.
 In addition the precursors used for producing the SnS compound are both abundant
in nature and with little toxicity.
 In thin film production, many methods have been used such as dc magnetron
sputtering , pulse electro-deposition method , thermal evaporation method ,
rfmagnetron sputtering , spray pyrolysis method and chemical bath deposition
method (CBD) .
 When CBD is compared with the above methods, it is relatively easier, more rapid
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and inexpensive. Moreover, by using this method, a film can be deposited on large
substrates irrespective of the shape and morphology of substrates nearly at room
temperature.
 In this work, we have examined the effect of deposition time on the properties
of SnS thin films.
 We have aimed to find out how deposition time effect the structural,
electrical, and optical properties of SnS thin films obtained by the CBD
method.
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Experimental
1M CH3CSNH2 5ml + 1M SnCl2·2H2O 5ml + NH4Cl 5ml
+ 3.75M N(CH2CH2OH)3 10ml + 0.66M C6H5Na3O7 5ml + DI Water 70ml
Final pH 9.31
Deposition time 2,4,6,8,10h and glass substrate 60°C
XRD、SEM、EDX、 Hall、 UV/VIS、 Thin film Stress Measure
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[Sn(TEA)]2++CH3CSNH2+2OH− → SnS+TEA+CH3CONH2+H2O
Results and discussion
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這張是SnS在不同沉積時間下的
XRD圖。
可以看出來除了2h為amorphous，
其餘皆為orthorhombic。
在沉積時間為4、6、8h，最強峰
皆為(110)，但在10h時，其最強峰
為(111)。
並且在4、6、8h時，也可以看到
(111)的Sn。
從這些XRD圖，可以看出來SnS
是由一組不同相的晶體所組成。
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這張是SnS(110)在不同沉積時間
下的所做的粒徑大小與紋理效應。
可以看出來隨著沉積時間由2h~6h，
其粒徑逐漸變大，然後在8h時又
變小，其原因可能是晶體間的互
相吸引與凡德瓦力所造成。
其紋理效應為1.6~2.4。
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這張是SnS在不同沉積時間下的單
位面積的晶體數量。
可以看出來，單位面積的晶體數
量隨著SnS的沉積時間增加而變多。
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這張是SnS在不同沉積時間
下的SEM。
可以看出來，隨著沉積時
間的增加，SnS的結構更均
勻。但是從沉積時間為6h，
可以看出來就算聚集很密
集還是有空隙；8h和10h是
一個多孔性結構。
從EDS分析來看，Sn/S比為
1.49，與實驗的Sn/S計量比
1高出許多。
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這張是利用霍爾效應來量
測SnS在不同沉積時間下的
電阻率變化。
其最佳的電阻率為SnS沉積
時間為6h。當沉積時間從
6h後，電阻率開始增加，
其原因是SnS尺寸變小和孔
隙的增加。
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這張是利用霍爾效應來量
測是SnS 6h沉積時間的導電
性變化。
可以看出來具有半導體特
性，導電性隨著溫度的提
高而增加。
從斜率可以算出活化能為
0.527eV。
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這張是SnS在不同沉積時間
下所量測到的穿透光譜。
可以看出來，沉積時間為
2h的穿透性最好。沉積時
間為6h的穿透性最差，其
原因可能是穿透性與薄膜
厚度及孔隙度有關。
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這張是SnS在不同沉積時間
下所量測到的反射光譜。
可以看出來，沉積時間6h
的反射性最佳，2h的反射
性最差，與穿透性符合。
由穿透性與反射性的圖來
看，SnS薄膜適合當太陽能
電池的吸收層。
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這張是SnS在不同沉積時間
下所量測到的允許、禁止、
直接、間接光學能隙。
可以看出來，
當沉積條件、基板溫度、
溶液濃度保持固定，其能
隙隨薄膜厚度變化而變化，
其原因可能是
(1)largeness of the
dislocation
(2) quantum size effect
(3) changing barrier height。
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在後續實驗將增加晶粒大
小、薄膜厚度及減少蕭特
基的障壁高度。
Conclusions
 SnS thin films were deposited onto glass substrates by using CBD in the deposition
time range of 2–10 h at 60 ◦C.
 The salient conclusions arising from this study are summarized below:
 (i) XRD analysis revealed the polycrystalline and orthorhombic structure of SnS thin
films.
 (ii) It was found that the grain size and texture coefficient increased from 22nm to
1.6–24nm and 2.4 with increasing deposition time from 2 h to 6 h except 8 h in
which they decreased to 20nm and 1.6, respectively. However, the number of
crystallites increased with increase in deposition time. It was inferred that films had
preferential orientation through (1 1 0) crystal plane from the values of texture
coefficient.
 (iii) EDX analysis showed that the film deposited had higher atomic ratio of Sn/S
(∼1.49).
 (iv) Hall Effect measurements showed that films had p-type electrical conductivity
and that the value of resistivity of SnS film was affected from the deposition time.
 (v) Activation energy value was found to be 0.527 eV.
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 (vi) Absorption coefficient value was found to be higher than 104 cm−1 in the
wavelength range of 190–1100 nm. Allowed direct transitions optical band gap
values were calculated in the range of 1.30–1.97 eV.
 (vii) It can be concluded that influence of the deposition time on the structural,
electrical, and optical properties of the films was determined.
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