Preparation of CIGS films by post-selenization of precursors Preparation of CIGS films by...
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Preparation of CIGS Preparation of CIGS films films by post-selenization of by post-selenization of precursors precursors Zs. Baji 1 , Z. Lábadi 1 , Gy. Molnár 1 Z. E. Horváth 1 , A.L. Tóth 1 , K. Vad 2 , I. Bársony 1 1 – Research Centre for Natural Sciences (MFA), Konkoly Thege M. út 29-33, H-1121 Budapest, HUNGARY 2.- Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI) H-4001 Debrecen, P.O. Box 51 Corresponding author: Z. Labadi, Email: [email protected], Tel: +36 1 3922225, Fax: +36 1 392 2226 Acknowledgement: The authors wish to thank the Hungarian National Science Fund OTKA (Grant No. NK 73424) for the support Experimental SEM morphology of the layers Conclusions Abstract The preparation of CIGS layers with post-selenization of precursors has been examined. Metallic precursors were evaporated consecutively and by flash evaporation. Two different selenization methods have been tested: annealing in Se atmosphere and evaporation of Se followed by post annealing. The optimal selenization method and proper order of evaporation has been established. The CIGS layers were deposited on Si and glass substrates both cleaned in cc.HNO3 and high purity water before deposition. Compositon of the precursor was always kept In:Ga:Cu/0,8:0,2:1. F lash evaporat ion : Cu, In and Ga were evaporated simultaneously from a single source at ~1x10 - 6 mbar background pressure. Estimated temperature of the source was between 1500-2000ºC S equential depositi t ion: Cu was deposited by pulsed DC magnetron sputtering from a metallic Cu target (10 µs cycle with 10% duty factor, 6*10 -3 mbar Ar working pressure at 50 sccm total gas inlet). The target power was 250W and the target voltage was 290V. In was evaporated at 1040-1060°C source temperature at pressure 2*10 -5 mbar, while Ga evaporation took place at 1115-1141°C and 1,7*10 -5 mbar respectively. Four sequences (i.e. Cu- In-Ga, Cu-Ga-In, In-Ga-Cu and Ga-In-Cu) were tested for post selenization. T wo diffe rent methods were applied for post selenization . - Evaporation of selenium from a W boat onto the top of the layers followed by an annealing - Annealing of the precursors in closed ampoules under Se atmosphere for 15 minutes at 500°C. •Flash evaporated and post-selenized layers showed a homogeneous CIGS structure after 10 minutes selenization. • The sequentially evaporated layers give the best result with the In+Ga+Cu deposition sequence • Precursor layer inhomogeneity (In and Ga droplets and islands) did not negatively affect the resulting CIGS layer. •No Ga accumulation was found at the back contact of the layers, the Ga concentration is uniform across the film thickness. Selenization in Se atmosphere resulted in homogeneous layers, with a cauliflower-like morphology (left picture). Within the layers the pyramid- like crystallites typical of the chalcopyrite phase are also visible (top right of the poster) Selenization in Se atmosphere results in ful selenization of the precursor In case of the consecutively evaporated layers where the copper was at the bottom, hexagonal crystallites are visible all over the surface (right). „Cu on top” sequence has to be preferred Typical EDS elemental map of the metallic precursors: islands of Ga and In are present „Cu on top” samples also shows ga droplets – Ga diffuses out durin Typical cross-sectional SEM micrograph of selenization with Se evaporation: Metallic sublayer is present at the bottom. Precursor depositon order Selenization Structure In+Ga+Cu Se evaporation and post annealing CuIn 0,7 Ga 0.3 Se 2 and CuInSe 2 phases with metallic In Ga+In+Cu Se evaporation and post annealing CuInSe 2 with some CuIn 0,7 Ga 0.3 Se2 and metallic In Cu+In+Ga Se evaporation and post annealing CuInSe 2 phase with (213) orientation, small grains, some Cu and In. Cu+Ga+In Se evaporation and post annealing CuInSe 2 with In and Cu In+Ga+Cu Se vapour at 500°C for 20 minutes CuIn 0,7 Ga 0.3 Se2 with a little CuInSe 2 phase present. Ga+In+Cu Se vapour at 500°C for 20 minutes CuInSe 2 with a little CuIn 0,7 Ga 0.3 Se 2 Cu+In+Ga Se vapour at 500°C for 20 minutes CuIn 0,9 Ga 0.1 Se 2 with some hexagonal CuSe. Cu+Ga+In Se vapour at 500°C for 20 minutes CuInSe 2 and CuIn 0,7 Ga 0.3 Se 2 with a little hexagonal CuSe Flash evaporated from one source Se vapour at 500°C for 5 minutes CuIn 0,8 Ga 0.2 Se 2 Flash evaporated from one source Se vapour at 500°C for 15 minutes CuIn 0,8 Ga 0.2 Se 2 Flash evaporated from one source Se vapour at 500°C for 20 minutes CuIn 0,7 Ga 0.3 Se 2 SNMS depth profiling (Cu, In, Ga, Se) phases found by XRD 0 100 200 300 400 500 600 700 800 0 20 40 60 80 100 D epth [nm ] C oncentration [at% ] Si Cu Ga In Se CuInGaSe2 layer prepared by flash evaporation SNMS depth profile of a flash evaporated sample – no Ga accumulation observable at the back contact XRD spectra of the flash evaporated samples post- selenized at 500°C. Only peaks of chalcopyrite structure are present, no oxides or other selenides are observable XRD characterization
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Transcript of Preparation of CIGS films by post-selenization of precursors Preparation of CIGS films by...
Preparation of CIGS Preparation of CIGS films films by post-selenization of precursorsby post-selenization of precursors Zs. Baji1, Z. Lábadi1, Gy. Molnár1 Z. E. Horváth1, A.L. Tóth1, K. Vad2, I. Bársony1
1 – Research Centre for Natural Sciences (MFA), Konkoly Thege M. út 29-33, H-1121 Budapest, HUNGARY 2.- Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI) H-4001 Debrecen, P.O. Box 51
Corresponding author: Z. Labadi, Email: [email protected], Tel: +36 1 3922225, Fax: +36 1 392 2226
Acknowledgement: The authors wish to thank the Hungarian National Science Fund OTKA (Grant No. NK 73424) for the support
Experimental
SEM morphology of the layers
Conclusions
Abstract
The preparation of CIGS layers with post-selenization of precursors has been examined. Metallic precursors were evaporated consecutively and by flash evaporation. Two different selenization methods have been tested: annealing in Se atmosphere and evaporation of Se followed by post annealing. The optimal selenization method and proper order of evaporation has been established.
The CIGS layers were deposited on Si and glass substrates both cleaned in cc.HNO3 and high purity water before deposition.Compositon of the precursor was always kept In:Ga:Cu/0,8:0,2:1.Flash evaporation: Cu, In and Ga were evaporated simultaneously from a single source at ~1x10-6 mbar background pressure. Estimated temperature of the source was between 1500-2000ºCSequential depositition: Cu was deposited by pulsed DC magnetron sputtering from a metallic Cu target (10 µs cycle with 10% duty factor, 6*10-3 mbar Ar working pressure at 50 sccm total gas inlet). The target power was 250W and the target voltage was 290V. In was evaporated at 1040-1060°C source temperature at pressure 2*10-5 mbar, while Ga evaporation took place at 1115-1141°C and 1,7*10-5mbar respectively. Four sequences (i.e. Cu-In-Ga, Cu-Ga-In, In-Ga-Cu and Ga-In-Cu) were tested for post selenization.Two different methods were applied for post selenization. - Evaporation of selenium from a W boat onto the top of the layers followed by an annealing - Annealing of the precursors in closed ampoules under Se atmosphere for 15 minutes at 500°C.
•Flash evaporated and post-selenized layers showed a homogeneous CIGS structure after 10 minutes selenization.
• The sequentially evaporated layers give the best result with the In+Ga+Cu deposition sequence
• Precursor layer inhomogeneity (In and Ga droplets and islands) did not negatively affect the resulting CIGS layer.
•No Ga accumulation was found at the back contact of the layers, the Ga concentration is uniform across the film thickness.
Selenization in Se atmosphere resulted in homogeneous layers, with a cauliflower-like morphology (left picture). Within the layers the pyramid-like crystallites typical of the chalcopyrite phase are also visible (top right of the poster)
Selenization in Se atmosphere results in ful selenization of the precursor
In case of the consecutively evaporated layers where the copper was at the bottom, hexagonal crystallites are visible all over the surface (right). „Cu on top” sequence has to be preferred
Typical EDS elemental map of the metallic precursors: islands of Ga and In are present
„Cu on top” samples also shows ga droplets – Ga diffuses out durin sputtering
Typical cross-sectional SEM micrograph of selenization with Se evaporation: Metallic sublayer is present at the bottom.
Precursor depositon order Selenization Structure
In+Ga+Cu Se evaporation and post annealing CuIn0,7Ga0.3Se2 and CuInSe2 phases with metallic In
Ga+In+Cu Se evaporation and post annealing CuInSe2 with some CuIn0,7Ga0.3Se2 and metallic In
Cu+In+Ga Se evaporation and post annealing CuInSe2 phase with (213) orientation, small grains, some Cu and In.
Cu+Ga+In Se evaporation and post annealing CuInSe2 with In and Cu
In+Ga+Cu Se vapour at 500°C for 20 minutes CuIn0,7Ga0.3Se2 with a little CuInSe2 phase present.
Ga+In+Cu Se vapour at 500°C for 20 minutes CuInSe2 with a little CuIn0,7Ga0.3Se2
Cu+In+Ga Se vapour at 500°C for 20 minutes CuIn0,9Ga0.1Se2 with some hexagonal CuSe.
Cu+Ga+In Se vapour at 500°C for 20 minutes CuInSe2 and CuIn0,7Ga0.3Se2 with a little hexagonal CuSe
Flash evaporated from one source Se vapour at 500°C for 5 minutes CuIn0,8Ga0.2Se2
Flash evaporated from one source Se vapour at 500°C for 15 minutes CuIn0,8Ga0.2Se2
Flash evaporated from one source Se vapour at 500°C for 20 minutes CuIn0,7Ga0.3Se2
SNMS depth profiling
(Cu, In, Ga, Se) phases found by XRD
0 100 200 300 400 500 600 700 8000
20
40
60
80
100
Depth [nm]
Con
cent
rati
on [
at %
]
Si Cu Ga In Se
CuInGaSe2 layer prepared by flash evaporation
SNMS depth profile of a flash evaporated sample – no Ga accumulation observable at the back contact
XRD spectra of the flash evaporated samples post-selenized at 500°C.
Only peaks of chalcopyrite structure are present, no oxides or
other selenides are observable
XRD characterization
