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¦ í ß –õ † < Æ@ /† < Æ „  l „   † < Æ Ò, Ö  ¦ í ß – 680-749

(2011¸   2 Z 4 16{ 9  ~ à Î6 £ §, 2011¸   3 Z 4 15{ 9  à º& ñ ‘ : r ~ à Î6 £ §, 2011¸   3 Z 4 27{ 9  > F  S X ‰& ñ )

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nanorod ~ à Ì} Œ •`  ¦ $ í  © œr v “ ¦, $ í  © œ  ) a nanorod ~ à Ì} Œ •_  ½ ¨› ¸& h  F  g † < Æ& h  : £ ¤$ í `  ¦ › ¸  % i  .

SEM õ  XRD › ¸   õ  buffer layer\  ¦ ¶ ú š{ 9 ô  Ç r « Ñ\  ¦ 600

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C \ " f \ P % ƒo  % i `  ¦ M : nanorod_  $ í  © œ s

 ¸ ú ˜ s À Ò# Q& ’ Ü ¼ 9 $ í  © œ  ) a nanorod _  U  ´s ü < ; Ÿ ¤“ É r y Œ •y Œ • 1000 nmü < 140 nm% i  . È Òõ Ö  ¦ Û ¼& 7 ˜à Ô! 3  ì 

r$ 3   õ  ~ à Ì} Œ •_  f  ¨ à º : £ ¤$ í “ É r \ P % ƒo \    É r   & ñ ½ ¨› ¸_     o\  _ ” > r % i “ ¦, f  ¨ à ºé ß –_  s 1 l x ¢ ¸ô  Ç › ' a

¹

1 Ï÷ &% 3  . : £ ¤ y  600

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C \ " f \ P % ƒo   ) a r « Ñ[ þ t \ " f  H Á º| 9 " fô  Ç rod $ í  © œ\  _ ô  Ç ³ ð€   í ß –ê ø Í_   H 7 £ x 

\

 _ K  ¢ - a ë ß –ô  Ç È Òõ Ö  ¦ _  y Œ ™™ è: £ ¤$ í `  ¦ ˜ Ð% i Ü ¼ 9, buffer layer ¶ ú š{ 9  ) a ~ à Ì} Œ •\ " f $ í  © œ  ) a nanorod ~ Ã Ì }

Œ

•_  F  g † < Æ& h   ½ ™× ¼ Ì “ s“ É r 2.28 eV% i  .

Ù þ

˜d ” # Q: Nanorod, V

2

O

5

, RF Û ¼( ' a A, F  g † < Æ& h  : £ ¤$ í

Structural and Optical Properties of V ₂ O ₅ Nanorod Films

Eunji Oh · Manil Kang · Sok Won Kim ^∗

Department of Physics, University of Ulsan, Ulsan 680-749

Hyo Yeol Park

Electronics and Communication Semiconductor Applications, Ulsan College, Ulsan 680-749 (Received 16 February 2011 : revised 15 March 2011 : accepted 27 March 2011)

V

2

O

5

nanorod films were grown, and the structural and the optical properties of the films were investigated. The results of FE-SEM and XRD investigations showed that the nanorods were well grown when a buffer layer was inserted and the films were post-annealed at 600

^◦

C. The length and the width of the nanorods were to be found approximately 1000 nm and 140 nm, respectively.

According to transmission spectra, the absorption of the films depended on the variation in the crystalline structure induced by post-annealing, and a shift of the absorption edge was observed.

Particularly, the samples post-annealed at 600

^◦

C showed a gentle decrease of thd transmittance due increased surface scattering caused by disordered growth of nanorods, and the optical band-gap energy of the nanorod film grown with an inserted buffer layer was 2.28 eV.

PACS numbers: 78.66.J, 61.46

Keywords: Nanorod, V

2

O

5

, RF sputtering, Optical property

∗

E-mail: [email protected] -362-

Fig. 1. (Color online) Cross-sectional structures of sam- ples; (a) As-grown V

2

O

5

film and (b) film inserted buffer layer.

I. " e  ] Ø

š

¸í ß – o  
´ o u(V

2

O

₅

)“ É r F  g  Ò  o$ í , F  g8 ú ¤ B ,  o† < Æ& h  G ' p d ç

1 p x õ  ° ú  “ É r „  l & h ,  o† < Æ& h , F  g † < Æ& h “   # Œ Q : £ ¤$ í [ þ t`  ¦

t “ ¦ e ” Ü ¼ 9 [1–5], „  s  “ : r • ¸(257

^◦

C)   H % ƒ\ " f ] X ƒ  

^

‰-F K5 Å q (metal-to-insulator transition)„  s  { 9 # Qè ß – .

V

₂

O

₅

_  q $ † ½ ӓ É r „  s  “ : r • ¸\  ¦ l ï  r Ü ¼– Ð / å L  y     o 

€

 " f ] X ƒ  ^ ‰\ " f F K5 Å q Ü ¼– Ð_  : £ ¤$ í    o { 9 # Qè ß –  [6].

s

 Qô  Ç : £ ¤$ í [ þ t M :ë  H \  ~ à Ì} Œ •+ þ A s  „  t  (thin film sec- ondary battery) [7], o ½ ¢ § s “ : r C ' o  (lithium battery), electrochromic/color memory, F  g„    Û ¼0 Au  1 p x _  „  l  F 

g † < Ɓ © œu  ì  r  \ " f_  ƒ  ½ ¨  Ö ¸ µ 1 Ï >  s À Ò# Qt “ ¦ e ”   [8,9].

V

2

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5

\   H α-V

2

O

5

(orthorhombic)`  ¦ Ÿ í† < Êô  Ç β-V

2

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5

(monoclinic or tetragonal) ü < γ-V

2

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5

(orthorhombic) ü <

° ú

 “ É r Y > Y > _    É r  © œ[ þ t s  ” > r F ô  Ç  [10–12]. : £ ¤ y  α- V

2

O

5

  H V

2

O

5

_  # Œ Q  © œ[ þ t ×  æ  © œ î ß –& ñ ô  Ç  © œs  9 Û ¼ (

' a AZ O \  _ K  ~ 1 >  % 3 `  ¦ à º e ”  . þ j   H \  V , “ É r q ³ ð

€

 & h `  ¦ ° ú   H
” ¸½ ¨› ¸ ~ à Ì} Œ •`  ¦ y Œ ™t  F « і Ð  6   x # Œ ± ú 

“ É

r 1 l x  Œ • “ : r • ¸
 „  · ú š\ " f• ¸  Å Ò ± ú “ É r 0 l x • ¸_  Û ¼[ þ t`  ¦ y

Œ

™t ½ + É Ã º e ”  . ¢ ¸ô  Ç
” ¸½ ¨› ¸ ~ à Ì} Œ •[ þ t`  ¦ s 6   x €   G ' p" f _

 ™ è+ þ A o 0 p x    H  © œ& h s  e ” # Q nanorod, nanowire, nanotube 1 p x õ  ° ú  “ É r q ³ ð€  & h s  B Ä º  H
” ¸½ ¨› ¸ ~ à Ì} Œ • [

þ

t _  $ í  © œõ  : £ ¤$ í \  @ /ô  Ç ƒ  ½ ¨  Ö ¸ µ 1 Ïy  ”  ' Ÿ ÷ &“ ¦ e ”   [13].

‘

: r ƒ  ½ ¨\ " f  H RF Û ¼( ' a AZ O Ü ¼– Ð V

2

O

₅

~ à Ì} Œ •`  ¦ ] j



Œ

• “ ¦, Ê ê\ P % ƒo \  ¦ : Ÿ x # Œ nanorod ~ à Ì} Œ •`  ¦ $ í  © œr (   .

~ Ã

Ì} Œ •_  $ í  © œ › ¸| õ  Ê ê\ P % ƒo  › ¸| \    É r nanorod _  $ í



© œ : £ ¤$ í `  ¦ › ¸  % i Ü ¼ 9, ¢ ¸ô  Ç, nanorod_  $ í  © œ › ¸| \ 



 É r ½ ¨› ¸& h  F  g † < Æ& h  : £ ¤$ í _     o\  @ / # Œ  7 H _  % i  .

II. ÷ m Ç] M öU ê s0 n É

Figure 1(a)  H  © œ“ : r \ " f l ó ø Í0 A\  { 9 ) €”   q & ñ | 9  V

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5

~ Ã

Ì} Œ •_  é ß –€   ½ ¨› ¸s “ ¦, Fig. 1(b)  H l ó ø ͓ : r • ¸ 500

^◦

C \ " f 7

£

x ‚ Ã Ì  ) a · û ª“ É r buffer layer\  ¦ ¶ ú š{ 9  “ ¦ Õ ª 0 A\  Fig. 1(a)ü <

1

l x{ 9 ô  Ç › ¸| Ü ¼– Ð q & ñ | 9  V

2

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5

~ à Ì} Œ •_  7 £ x ‚ à Ì`  ¦ & ñ ô  Ç r 

«

Ñ_  é ß –€   ½ ¨› ¸s  . ~ à Ì} Œ •_  ¿ ºa   H ì  rF  g  " é ¶ >  (Spec- troscopic Ellipsometer) – Ð 8 £ ¤& ñ % i  . 7 £ x ‚ Ã Ì  ) a ~ à Ì} Œ •_  ¿ º a

  H €  • 200 nms “ ¦, buffer layer_  ¿ ºa   H €  • 140 nm% i 



. ~ à Ì} Œ •“ É r RF Û ¼( ' a AZ O `  ¦ s 6   x # Œ  
´ o u   ¿ (pu- rity 99.7 %) \  Arõ  O

²

Û ¼\  ¦ Å Ò{ 9  # Œ e  ¦  Ý ¼ \  ¦ + þ A

$ í

r &  ] j Œ • % i  . Û ¼( ' a A „  \  Al

2

O

3

l ó ø Í`  ¦ · ú ˜ ï`  ¦

–

Ð [ j' ‘ ô  Ç  6 £ § | 9 ™ è\  ¦ Ô  ¦ # Q L :  F M >  % i  . ' ˜ Ð* 3 á Ô

\

 ¦ s 6   x # Œ 5 × 10

⁻⁶

Torr  t  œ íl  ”  / B N  © œI \  ¦ ë ß –Ž  H



6 £ §, Ar õ  O

²

Û ¼\  ¦ { 9 & ñ >  Õ þ ›! Q ? /– Ð Å Ò{ 9 r v €  

"

f 70 W_  RF  0 >\  ¦ / B N/ å L # Œ e  ¦  Ý ¼ \  ¦ µ 1 ÏÒ q tr (   .

s

M : Å Ò{ 9 ô  Ç Û ¼_  € ª œ“ É r Ar“ É r 21 sccm, O

2

  H 9 sccm s 

%

3  . l ó ø ͓ : r • ¸  H  © œ“ : r õ  500

^◦

C – Ð % i Ü ¼ 9, Ê ê\ P % ƒo 



 H í ß –™ è ì  r 0 Al \ " f y Œ •y Œ • 500

^◦

C ü < 600

^◦

C – Ð 150ì  r 1 l x î ß – È

ÓÚ Ô+ þ A „  l – Ð ? /\ " f ”  ' Ÿ  % i  . Table 1\  ] j Œ •  ) a r 

«

Ñ[ þ t _  ½ ¨› ¸ü < Ê ê\ P % ƒo  › ¸| `  ¦
 ? /% 3  . Table 1\ 

"

f sample 1, 3, 5  H Fig. 1(a) ü < ° ú  s  Al

²

O

3

l ó ø Í 0 A\   © œ

“

: r \ " f 150ì  r 1 l x î ß – q & ñ | 9  V

2

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5

~ à Ì} Œ •ë ß – 7 £ x ‚ à Ìô  Ç 18 £ x ~ Ã Ì }

Œ

•s  . Fig. 1(b)ü < ° ú  “ É r ~ à Ì} Œ •“   sample 2, 4, 6“ É r Al

2

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3

l

ó ø Í\    & ñ | 9 _  buffer layer V

²

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5

~ à Ì} Œ •`  ¦ 7 £ x ‚ Ã Ì “ ¦ Õ ª 0

A\  q & ñ | 9  V

₂

O

₅

~ à Ì} Œ •`  ¦ 7 £ x ‚ à Ìô  Ç 28 £ x ~ à Ì} Œ •s  .   & ñ | 9  V

2

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5

buffer layer  H Al

2

O

3

0 A\  l ó ø ͓ : r • ¸\  ¦ 500

^◦

C – Ð 

#

Œ 60ì  r 1 l x î ß – 7 £ x ‚ à Ìô  Ç  כ s “ ¦, q & ñ | 9  V

₂

O

₅

  H buffer layer 0

A\   © œ“ : r \ " f 150ì  r 1 l x î ß – 7 £ x ‚ à Ìô  Ç  כ s  .

Ê

ê\ P % ƒo \    É r ~ à Ì} Œ •[ þ t _  ³ ð€    © œI _     o\  ¦ › ¸   l

0 AK  FE-SEM (JSM-6500F, JEOL)`  ¦ s 6   x # Œ r « Ñ [

þ

t _  ³ ð€  `  ¦ 15 8 _  4 Ÿ ¤  – РÒ'  20,000C _  C Ö  ¦ – Ð r 

«

Ñ[ þ t _  ³ ð€  `  ¦ › ' a ¹ 1 Ï % i  . r « Ñ_    & ñ ½ ¨› ¸\  ¦ › ¸   l

0 AK  XRD (D/MAX-RC, Rigaku)\  ¦  6   x % i Ü ¼ 9,  r ] X

 J ‡  “ É r 30 kV, 60 mA, Cu K

α

(1.5406 ˚ A) _  4 Ÿ ¤  – ÐÂ Ò '

 % 3 % 3  .  r] X J ‡  “ É r 2θZ O Ü ¼– Ð 15 ∼ 60

^◦

 t  ì  r { © œ 4

^◦

5

Å

q • ¸\ " f 0.02

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ç ß –  Ü ¼– Ð 8 £ ¤& ñ % i  . Ê ê\ P % ƒo  „  Ê ê_  È

Òõ Ö  ¦    o\  ¦ › ¸  l 0 AK  UV/VIS ì  rF  gF  g • ¸> (8453, HP)\  ¦  6   x % i Ü ¼ 9, 190 ∼ 1100 nm_    © œ% ò % i \     5

g 1 nm ç ß –  Ü ¼– Ð 8 £ ¤& ñ % i “ ¦, 8 £ ¤& ñ { 9  y Œ •“ É r 0

^◦

– Ð “ ¦& ñ

% i  .

Table 1. Structures and post-annealing conditions of samples.

Annealing Annealing Sample Structure Temperature Time

(

^◦

C) (minute) 1 without buffer layer

2 with buffer layer · ·

3 without buffer layer

4 with buffer layer 500

5 without buffer layer 150 6 with buffer layer 600

III. + s ÇÊ Ý õ m Í À X Ø8 ý

1.  Œ ºX ì Ä — ¤V R Ë

Figure 2  H  € ª œô  Ç “ : r • ¸\ " f Ê ê\ P % ƒo   ) a V

₂

O

₅

nanorod ~ à Ì} Œ •_  ³ ð€   SEM  ”  s  . Figures 2(a)-2(f)  H r

« Ñ (1)-(6)_  í  H " fü < 1 l x{ 9   . Figure 2(a)  H q & ñ | 9  V

2

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5

~ à Ì} Œ •s “ ¦, Fig. 2(b)  H buffer layer  ¶ ú š{ 9   ) a ~ à Ì} Œ • s

 9, ¿ º  ”  _  [ j– Ð ~ ½ ӆ ¾ ӓ É r Ê ê\ P % ƒo  “ : r • ¸    o\    É r

³

ð€   SEM  ”  s  . Fig. 2(c)ü < 2(e)  H 500

^◦

C \ " f, Fig.

2(d) ü < 2(f)  H 600

^◦

C \ " f Ê ê\ P % ƒo   ) a  כ s  . : £ ¤ y  600

◦

C \ " f \ P % ƒo   ) a ~ à Ì} Œ •[ þ t _  ³ ð€  \ " f Ì º§  ô  Ç nanorod ½ ¨

›

¸ S X ‰ “  ÷ &% 3 Ü ¼ 9, buffer layer ¶ ú š{ 9  ) a ~ à Ì} Œ •\ " f $ í



© œ  ) a } Œ •@ / (rod)_  U  ´s ü < ; Ÿ ¤“ É r y Œ •y Œ • €  • 1000 nmü < 140 nm% i “ ¦, q & ñ | 9  ~ à Ì} Œ •_  } Œ •@ / (rod) ; Ÿ ¤“ É r €  • 10 ∼ 20 nm

&

ñ • ¸  8 ¿ º  ° ? . SEM 8 £ ¤& ñ   õ  buffer layer\  ¦ ¶ ú š{ 9 ô  Ç q

& ñ | 9  ~ à Ì} Œ •s  Ê ê\ P % ƒo  ÷ &% 3 `  ¦ M : nanorod_  $ í  © œs  ˜ Ð



 ¸ ú ˜ s À Ò# Q & ’ Ü ¼ 9, s  Qô  Ç   õ   H nanorod  $ í  © œ½ + É M

: l ó ø Í_    & ñ ½ ¨› ¸\  ß ¼>  _ ” > r ô  Ç   H  כ `  ¦ _ p ô  Ç .

Figure 3“ É r Ê ê\ P % ƒo \    É r q & ñ | 9  V

₂

O

5

~ à Ì} Œ •_  XRD J ‡  s  . XRD 8 £ ¤& ñ   õ  r « Ñ 1õ  2_    & ñ ½ ¨› ¸



 H q & ñ | 9 – Ð S X ‰ “  ÷ &% 3  . r « Ñ 3õ  4  H €  • 20.54

^◦

  H % ƒ

\

" f α-V

2

O

₅

(001)€  \  @ /6 £ x   H y © œô  Ç x ß ¼
 z Œ ¤Ü ¼ 9, ¢ ¸ô  Ç 41.33

^◦

  H % ƒ\ " f  H €  •ô  Ç α-V

₂

O

5

(002)€  \  @ /ô  Ç x

ß ¼ › ' a ¹ 1 Ï÷ &% 3  . r « Ñ 5ü < 6 ¢ ¸ô  Ç α-V

₂

O

₅

(001)€  õ  (002)€  \  @ /ô  Ç x ß ¼
 z Œ ¤Ü ¼ 9 r « Ñ 6\ " f  H 27.65

^◦

Â

Ò   H \ " f α-V

2

O

₅

(110)€  \  @ /ô  Ç x ß ¼• ¸ › ' a ¹ 1 Ï÷ &% 3  .

600

^◦

C \ " f Ê ê\ P % ƒo   ) a r « Ñ 5ü < 6_   â Ä º nanorod_ 

$ í

 © œs   Å Ò ¸ ú ˜ ÷ &% 3 6 £ § \ • ¸ Ô  ¦ ½ ¨ “ ¦ 500

^◦

C \ " f Ê ê\ P 

%

ƒo   ) a r « Ñ 3õ  4\  q K   © œ@ /& h Ü ¼– Ð €  •ô  Ç  r] X  x ß ¼\  ¦

˜

Ð% i  . s  Qô  Ç   õ   H SEM   õ \ " f ˜ Ð# Œt 1 p w s  Á º| 9 

"

fô  Ç rod $ í  © œ\  _ ô  Ç X-ray í ß –ê ø Í_  7 £ x  M :ë  H Ü ¼– Ð Ò q ty Œ •

 ) a  .

Fig. 2. (Color online) Structures morphologies of sam- ples; (a) As-grown film, (b) film inserted buffer layer, ((c) and (d)) post-annealed films at 500

^◦

C, and ((e) and (f)) post-annealed films at 600

^◦

C.

Fig. 3. (Color online) XRD patterns of as-deposited and

post-annealed films; ((1) and (2)) not-annealed, ((3) and

(4)) post-annealed films at 500

^◦

C, ((5) and (6)) post-

annealed films at 600

^◦

C.

Fig. 4. (Color online) Transmission spectra of samples;

The V

₂

O

₅

films on Al

₂

O

₃

substrates as a function of annealing temperature.

2. ° Ë Ñ] K ¡X ì Ä — ¤V R Ë

Figure 4  H ] j Œ •  ) a r « Ñ[ þ t _  È Òõ Ö  ¦ Û ¼& 7 ˜à Ô! 3 s  . r 

«

Ñ 1“ É r 580 ∼ 1100 nm _    © œ% ò % i \ " f €  • 82 % s  © œ_  È

Òõ Ö  ¦`  ¦ ˜ Ð% i Ü ¼ 9, r « Ñ 2  H 73 %, r « Ñ 3“ É r 70 %, r « Ñ 4  H 53 % s  © œ_  È Òõ Ö  ¦`  ¦ y Œ •y Œ • ˜ Ð% i “ ¦, y Œ •y Œ •_  r « Ñ[ þ t

“ É

r — ¸¿ º €  • 570 nm s  \ " f / å L  ô  Ç È Òõ Ö  ¦ _  y Œ ™™ è\  ¦ ˜ Ð

%

i  . r « Ñ 5ü < r « Ñ 6_  È Òõ Ö  ¦“ É r   É r r « Ñ[ þ t \  q K  ß

¼>  y Œ ™™ è % i Ü ¼ 9 450 nm s  © œ_  % ò % i \ " f ¢ - a ë ß –ô  Ç y Œ ™

™

è\  ¦ ˜ Ð% i  . 500

^◦

C \ " f Ê ê\ P % ƒo   ) a r « Ñ[ þ t _  f  ¨ à ºé ß –

“ É

r \ P % ƒo  „  _  r « ј Ð  é ß –  © œ A á ¤ Ü ¼– Ð s 1 l x % i “ ¦, f  ¨ Ã

ºé ß –_  l Ö  ¦ l   H ˜ Ð  / å L  K & ’  . t ë ß – 600

^◦

C \ " f

\ P

% ƒo   ) a r « Ñ[ þ t \ " f  H / å L  ô  Ç È Òõ Ö  ¦ _  y Œ ™™ è  H
 
 t

 · ú §€ Œ ¤ . s  Qô  Ç   õ [ þ t“ É r \ P % ƒo  “ : r • ¸ 7 £ x † < Ê\   



 ~ à Ì} Œ •_    & ñ ½ ¨› ¸ q & ñ | 9 \ " f   & ñ | 9 – Ð ß ¼>    Ù þ ¡ l

 M :ë  H s  9, s  Qô  Ç   & ñ ½ ¨› ¸_     o ~ à Ì} Œ •_  f  ¨ à º : £ ¤

$ í

`  ¦ ß ¼>  y © œ or †    כ Ü ¼– Ð Ò q ty Œ •  ) a  . ¢ ¸ô  Ç 600

^◦

C \ " f

\ P

% ƒo   ) a r « Ñ[ þ t \ " f_  È Òõ Ö  ¦ _   H y Œ ™™ èü < „  ^ ‰ % ò % i 

\

" f_  ¢ - a ë ß –ô  Ç y Œ ™™ è : £ ¤$ í “ É r nanorod $ í  © œ\  _ ô  Ç ³ ð€   í

ß –ê ø Í_   H 7 £ x  M :ë  H Ü ¼– Ð Ò q ty Œ •  ) a  .

Figure 5  H È Òõ Û ¼& 7 ˜à Ô! 3 \  _ K  % 3 # Q”   r « Ñ[ þ t _  F  g

†

< Æ& h   ½ ™× ¼ Ì “ s\  @ /ô  Ç Õ ªa Ë >s  . r « Ñ[ þ t _   ½ ™× ¼ Ì “ s“ É r Tauc law`  ¦ s 6   x ô  Ç ü @¶ ú š (extrapolation)\  _ K    & ñ ÷ &% 3   [14]. V

2

O

5

  H ∼2.3 eV & ñ • ¸_   ½ ™× ¼ Ì “ s \  -t \  ¦ ° ú   H ç ß – ] X

 „  s + þ A n+ þ A ì ø ͕ ¸^ ‰s  .

‘

: r ƒ  ½ ¨\ " f  H (αhν)

^1/2

= A

^1/2

(E − E

_g

)`  ¦ s 6   x ô  Ç þ j

&

h ´ ú » ¡ §`  ¦ : Ÿ x K  r « Ñ[ þ t _  F  g † < Æ& h   ½ ™× ¼ Ì “ s`  ¦   & ñ % i  .

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Fig. 5. (Color online) Optical band-gap energies of sam- ples: ((1) and (2)) as deposited films, ((3) and (4)) an- nealed films at 500

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C, ((5) and (6)) annealed films at 600

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C; ((3) and (5)) without buffer layer, ((4) and (6)) with buffer layer.

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h   ½ ™× ¼ Ì “ s“ É r y Œ •y Œ • 2.23, 2.28 eV% i  . SEMõ  XRD › ¸



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5

nanorod ~ à Ì} Œ •_  Û ¼ x 9   o† < Æ& h  G ' p

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f– Ð" f 6 £ x6   x l  0 Aô  Ç ƒ  ½ ¨\  ×  æ כ ¹ô  Ç  « і Ð s 6   x| ¨ c à º e ”

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c p 8 ý ò k >

s

  7 Hë  H“ É r 2009¸   & ñ  Ò(“ §¹ ¢ ¤ õ † < Æl Õ ü t  Ò)_  F " é ¶ Ü ¼– Ð ô

 Dz D Gƒ  ½ ¨F é ß –_  @ /† < Æ×  æ& h ƒ  ½ ¨™ è t " é ¶  \ O Ü ¼– Ð Ã º' Ÿ  ) a

ƒ

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Y

c p w Š à U Ø ”  ô

[1] C. W. Zou, X. D. Yan, D. A. Patterson, E. A. C.

Emanuelsson, J. M. Bian and W. Gao, CrystEng- Comm. 12, 691 (2010).

[2] Y. Hu, Z. Li, Z. Zhang and D. Meng, Appl. Phys.

Lett. 94, 103107 (2009).

[3] C. W. Zou, X. D. Yan, J. Han, R. Q. Chen and W.

Gao, J. Phys. D: Appl. Phys. 42, 145402 (2009).

[4] A. Talledo and C. G. Granqvist, J. Appl. Phys. 77, 4655 (1995).

[5] S. Teranishi and K. Tarama, J. Chem. Phys. 27, 1217 (1957).

[6] E. E. Chain, Appl. Opt. 30, 2782 (1991).

[7] Y. J. Park, J. G. Kim, M. K. Kim, H. T. Chung and H. G. Kim, J. Power Sources 87, 69 (2000).

[8] A. D. Raj, T. Pazhanivel, P. S. Kumar, D. Man- galaraj, D. Nataraj and N. Ponpandian, Curr. Appl.

Phys. 10, 531 (2010).

[9] M. W. Ahn, K. S. Park, J. H. Heo, J. G. Park, D. W.

Kim, K. J. Choi, J. H. Lee and S.-H. Hong, Appl.

Phys. Lett. 93, 263103 (2008).

[10] A. A. Akl, Appl. Surf. Sci. 253, 7094 (2007).

[11] R.-P. Blum, H. Niehus, C. Hucho, R. Fortrie, M. V.

Ganduglia-Pirovano, J. Sauer, S. Shaikhutdinov and H. J. Freund, Phys. Rev. Lett. 99, 226103 (2007).

[12] N. Fateh, G. A. Fontalvo, L. Cha, T. Kl¨ unsner, G.

Hlawacek, C. Teichert and C. Mitterer, Surf. Coat.

Technol. 202, 1551 (2008).

[13] P. Singh and D. Kaura, J. Appl. Phys. 103, 043507 (2008).

[14] J. Tauc, Optical Properties of Solids (North-

Holland, Amsterdam, 1972), p. 277.