12 Z 4, pp. 1231∼1246
V ê
s Æ X Ø V R Ë my ¢= kÀ W ¥ ÷ m Ç ô ÷ s Ú Ö « X ¢?
Ð ÷ 7 B¾ 6 Ò
Â
Òí ß @ / < Æ § ¸õ < Æl Õ ü t @ / < Æ BK21 ¸Ö 6 x ½ + Ë \ O é ß , x 9 ª 627-706
T
û B0 å · » 4 w H# Ü · + ä : c* å
Â
Òí ß @ / < Æ § t B j à Ô Ð_ Û ¼/ B N < Æõ , x 9 ª 627-706
»¬ £<
Â
Òí ß @ / < Æ § é ß & ñ É r' ½ ¨ è, x 9 ª 627-706
,
>
ø ¶ B' Ö < · ¬ £* å
Â
Òí ß @ / < Æ § ¸õ < Æl Õ ü t @ / < Æ ¸Ö 6 x ½ + Ël Õ ü t < Æõ , x 9 ª 627-706
T
g ` @+ Ö <
University of California, Berkeley, Berkeley, CA 94720-7300, U.S.A.
Ð= ÷ 7 B
Â
Òí ß @ / < Æ § ¸õ < Æl Õ ü t @ / < Æ ¸B jn ( / B N < Æõ , x 9 ª 627-706 (2010¸ 11 Z 4 30{ 9 ~ Ã Î6 £ §, 2010¸ 12 Z 4 10{ 9 > F S X & ñ )
Co ¸i ç ) a ZnO (ZnCoO) H % 6 £ § © : r y © $ í : £ ¤$ í s Ð ¦ ) a s Ê ê @ /³ ð& h ZnO l ì ø Í_ Ó ü É r
$ í
ì ø Í ¸^ (diluted ferromagnetic semicondutor, DMS) Ó ü t| 9 Ð" f ´ ú § É r ½ ¨ | 9 × æ ÷ &# Q M ® o . í ß \ O & h 3
l q& h Ü ¼ Ð H © : r \ " f y © $ í ` ¦ ° ú H ì ø Í ¸^ ] X z ´y 9 כ ¹ t ë ß # y © : r y © $ í _ " é ¶ õ y ©
$ í
B > h B j& m 7 £ § Õ ªo ¦ & ñ S X ô Ç l & h : £ ¤$ í \ @ /ô Ç 7 H ê ø Ís > 5 Å q ÷ & ¦ e Ü ¼ 9 Õ ª & ñ S X ô Ç l & h : £ ¤
$ í
\ @ /K f ¸ ¢ - a y ½ ©" î ÷ &t 3 l w ô Ç כ Ü ¼ Ð ~ à Π[ þ t # t ¦ e . : r ½ ¨\ " f H ZnCoO ¸ì r
´ ú
õ ¸~ à Ì} \ @ /K ½ ¨ ¸ü < l & h : £ ¤$ í ` ¦ ^ > & h Ü ¼ Ð ½ ¨ ¦ Co ' aº s © s y © $ í _ " é ¶ Ü
¼ Ð H â Ä ºü < Õ ªX O t · ú § É r â Ä º\ ¦ " î S X y µ 1 ß+ À I . ZnCoO\ à º è Å Ò{ 9 | ¨ c â Ä º Co-H-Co complex + þ A$ í ÷ &# Q y © $ í : £ ¤$ í ` ¦ ? / 9 ü @ Ò\ " f_ à º è Å Ò{ 9 õ Æ ÒØ ¦` ¦ : x K F & ³$ í e H y ©
$ í : £ ¤$ í ` ¦ % i & h Ü ¼ Ð ¸] X ½ + É Ã º e 6 £ §` ¦ Ð% i ¦, Ù þ x 9 ¸ ì r í ¸ \ ¦ : x K à º è Co-Co s _ antibonding site \ 0 Au < Ê` ¦ µ 1 ß+ À I . : r ½ ¨\ " f s 6 x ô Ç l Z O É r à º è_ ¸] X ` ¦ : x K $ í _ ß ¼l ¸ ] X
¸ 0 p x t ë ß : £ ¤ y Ê ê% o \ ¦ : x K × þ & h ² D G è % ò % i _ o e _ Ð 0 p x Ù ¼ Ð B j ¸o è
l ï× ¼ 1 p x ª ô Ç ì r \ 6 £ x6 x s 0 p x ½ + É כ s .
Ù þ
d # Q: Ã º èB > h y © $ í , ïµ 1 Ïà Ô ¸i ç ) a í ß o , Ó ü É r $ í ì ø Í ¸^ , l s ©
Seeking for Room Temperature Ferromagnetic Semiconductors Based on ZnO
Yong Chan Cho
Team of BK21 Nano Fusion Technology, Pusan National University, Miryang 627-706
-1231-
Seunghun Lee · Won-Kyung Kim · Se-Young Jeong ∗
Cogno-Mechatronics Engineering, Pusan National University, Miryang 627-706
Su Jae Kim
Crystal Research Institute, Pusan National University, Miryang 627-706
Jong Moon Shin · Su -Young Cha
Nano Fusion Technology, Pusan National University, Miryang 627-706
Hyun Jun Lee
University of California, Berkeley, Berkeley, CA 94720-7300, U.S.A.
Chae Ryong Cho
Nano Medical Engineering, Pusan National University, Miryang 627-706 (Received 30 November, 2010 : accepted 10 December, 2010)
Since the report of ferromagnetism in transition-metal-doped ZnO, Co-doped ZnO (ZnCoO), one of the most promising materials, has been extensively studied for realizing room-temperature ferromagnetism in diluted magnetic semiconductors(DMSs). Despite the tremendous potential for spintronic applications of ZnO-based DMS materials, it is not yet clear whether the ferromagnetism is an intrinsic property of the DMS or an extrinsic property resulting from the presence of defects, impurities, and inclusions. In this review, systematic investigations of the structural and the mag- netic characteristics clearly revealed the relation of ferromagnetism to magnetic secondary phases in ZnCoO nano powders and thin films. We propose Co-H-Co complexes as the origin of the fer- romagnetism in ZnCoO, which agrees well with the nuclear density distributions obtained from a MEM/Rietveld analysis of neutron and X-ray scattering. Furthermore, we show a reversible and reproducible change of ferromagnetism due to hydrogenation and dehydrogenation. These results can be applied to developing new functional memory devices and nano-scaled magnetic bar-codes by using a selective hydrogenation process to manipulation the spin ordering.
PACS numbers: 79.60.Bm
Keywords: Hydrogen mediated ferromagnetism, Co-doped ZnO, Dilute magnetic semiconductor, Magnetic secondary phase
I. " e  ] Ø
z
´o B H` ¦ l ì ø ÍÜ ¼ Ð H ì ø Í ¸^ è ü < { 9 7 à Ô
Ð_ Û ¼ (electronics) H & ñ Ð $ © 0 p x§ 4 _ 7 £ x @ /ü < % o 5 Å q
¸_ ¾ Ó © ` ¦ s µ ¡ ¤ 9 / å L y µ 1 Ï % i Ü ¼ 9, & ³F ¦ ¸
o ) a & ñ Ð o r_ H ç ß s ÷ &% 3 . Õ ª Q ¦x 9 ¸ | 9
&
h o l Õ ü t _ µ 1 Ï s ô Ç> \ ] X H < Ê\ _ ü
< Û ¼ 2 ;` ¦ < Êa ¸ x 9 ¸] X ½ + É Ã º e H l Õ ü t s כ ¹½ ¨÷ &
¦ e Ü ¼ 9 è0 A “Û ¼ 2 ;à Ô Ð_ Û ¼ (spintronics)” H < Æë H s
ß ¼> µ 1 Ï ¦ e . Û ¼ 2 ;à Ô Ð_ Û ¼ H _ ü <
< Êa _ ª % i < Æ& h $ í | 9 Û ¼ 2 ;(spin)` ¦ 6 x
∗
Corresponding author E-mail: [email protected]
H Û ¼ 2 ; { 9 7 à Ô Ð_ Û ¼ (spin electronics) ¦ ½ + É Ã º e
. [ j> & h Ü ¼ Ð ª ô Ç ½ ¨ì r \ " f Û ¼ 2 ; Å Ò{ 9 (spin injection), Û ¼ 2 ; à º5 Å x (spin transport), Û ¼ 2 ; ¸ õ ¸] X (spin control & manipulation), Û ¼ 2 ; ¼ # F g (spin polariza- tion), Û ¼ 2 ; y t (spin detector) 1 p x Û ¼ 2 ;` ¦ 6 x ô Ç D h Ð î
r Ó ü t$ í õ è _ > hµ 1 Ï` ¦ 0 Aô Ç ´ ú § É r ½ ¨ Ö ¸ µ 1 Ïy à º'
÷ & ¦ e [1,2]. s × æ \ " f ¸ l & h , F g < Æ& h : £ ¤$ í s 8 A
#
Qè ß ì ø Í ¸^ ? /\ ´ òÖ ¦& h Ü ¼ Ð Û ¼ 2 ;` ¦ Å Ò{ 9 H l Õ ü t É r D
h Ðî r Û ¼ 2 ; è \ ¦ > hµ 1 Ï H × æ כ ¹ô Ç ½ ¨ Ð Â Òy ÷ &% 3
. íl \ H Û ¼ 2 ; Å Ò{ 9 ` ¦ 0 AK y © $ í s F K5 Å q8 £ x (Fe, Co, Ni 1 p x) s 6 x ÷ &% 3 t ë ß F K5 Å q õ ì ø Í ¸^ _ > \ " f Û
¼ 2 ; + '| 9 j Ë µ í ß ê ø Í & ³ © (spin-flip scattering)s µ 1 ÏÒ q t # Û
¼ 2 ; Å Ò{ 9 \ ´ ú § É r ë H ] j µ 1 ÏÒ q t % i . s Qô Ç ë H ] j& h ` ¦
F
G4 ¤ ¦ ü < Û ¼ 2 ;` ¦ 1 l x r \ Ö ¸6 x # Û ¼ 2 ;-µ 1 Ï F g è
(spin-LED), Û ¼ 2 ;-à Ô ½ t Û ¼' (spin-transistor) 1 p x _ Û ¼
2 ; l ì ø Í (spin-based)_ D h Ðî r è \ ¦ > hµ 1 Ï l 0 A
# t è ß z # ¸ 1 l x î ß © : r \ " f y © $ í : £ ¤$ í ` ¦ ? /
H ì ø Í ¸^ Ó ü É r $ í ì ø Í ¸^ (diluted magnetic semicon- ductor, DMS) \ @ /ô Ç ´ ú § É r ½ ¨ | 9 × æ ÷ &# Q M ® o [1–12].
$ í ì ø Í ¸^ Ó ü t| 9 \ " f H Å Ò Ð s F K5 Å q(transition metal, TM) s : r s ì ø Í ¸^ ? /\ ª s : r` ¦ u ¨ 8 K [ þ t # Q> ÷ &
¦ s F K5 Å q _ d-C ¸_ f ± t · ú § H (lone pair elec- tron) _ 6 x Ü ¼ Ð ì ø Í ¸^ _ H o # Q(carrier)1 p x` ¦ Û ¼ 2 ; ¼ # F
g r & y © $ í ` ¦ Ä » ¸ ¦ % i . { 9 ì ø Í& h Ü ¼ Ð, DMS _
: £ ¤$ í ` ¦ % 3 l 0 AK " f H u ¨ 8 ÷ & H s F K5 Å q s : r _ 0 l x
¸ H B Ä º Z } " f ì ø Í ¸^ \ " f_ 6 x K ¸ ô Ç> (solubility limit)\ ¦ íõ H כ s @ /Â Òì r s . ì ø Í ¸^ \ " f Û ¼ 2 ; Å Ò { 9
õ Û ¼ 2 ; ¼ # F g : £ ¤$ í 1 p x _ DMS: £ ¤$ í ` ¦ ½ ¨ l 0 AK
"
f H ì ø Í ¸^ ? /\ " f_ s F K5 Å q $ 3 Ø ¦ (precipitation) 1 p x
`
¦ ] j H כ s 9 Ã º& h s . y © $ í s F K5 Å q _ $ 3 Ø ¦ õ
D h Ðî r s © (secondary phase)\ " f l H y ©
$ í
: £ ¤$ í É r DMS _ Û ¼ 2 ; ¼ # F g \ _ ô Ç ¦Ä »ô Ç (intrinsic) DMS : £ ¤$ í õ ½ ¨ì r ÷ & 9 DMS_ ¦Ä »ô Ç Ó ü t$ í ½ ¨\ " f 9 Ã
º& h Ü ¼ Ð C ] j÷ &# Q ô Ç . z ´] j Ð t F K t s © \ _
ô Ç y © $ í \ _ K q 2 © ÷ & H ¸í H ) a õ ü < 7 H ê ø Ís e
#
Q M ® o . t F K t _ DMS Ó ü t| 9 > hµ 1 Ï` ¦ 0 Aô Ç ´ ú § É r ¸§ 4
\
¸ Ô ¦ ½ ¨ ¦, þ j H t [ j> & h Ü ¼ Ð / B N ) a DMS Ó ü t
| 9
É r GaMnAs, InMnAs, GaMnSb 1 p x` ¦ í < Êô Ç F G èà º
Ð ] jô Ç÷ &# Q e . t ë ß s Qô Ç Ó ü t| 9 [ þ t _ B Ä º ± ú É r Ç
©o (Curie) : r ¸ Ð K , © : r \ " f_ 6 £ x6 x õ è > hµ 1 Ï
\
´ ú § É r # Q 9¹ ¡ § s e . t ë ß ZnOü < GaN 1 p x _ V , É r {
ç ß ì ø Í ¸^ (wide bandgap semiconductor) \ " f © : r y
© $ í ì ø Í ¸^ ½ ¨ & ³s 0 p x ½ + É כ s H > í ß õ Ð
¦ ) a Ê ê © : r \ " f 6 £ x6 x 0 p x ô Ç DMS Ó ü t| 9 \ @ /ô Ç ½ ¨
| 9 × æ& h Ü ¼ Ð r ÷ &% 3 [12–14].
II-VI7 á ¤ DMS Ó ü t| 9 × æ \ " f ZnO H Ó ü t| 9 ^ t H 8
A# Qè ß l & h -F g < Æ& h Ó ü t$ í Ü ¼ Ð K { 9 n  Ò' DMS
½
¨\ " f ´ ú § É r ' a d ` ¦ ~ Ã Î M ® o . : £ ¤ y , Co ¸i ç ) a ZnO (ZnCoO) \ " f_ © : r y © $ í s Ð ¦ ) a Ê ê ZnCoO H ©
: r y © $ í ½ ¨\ " f @ /³ ð& h Ó ü t| 9 Ð < Hg 1 L y ¦ e [15–
17]. t ë ß ´ ú § É r ½ ¨ [ þ t _ z ´+ « >& h 7 £ x õ s : r& h > í
ß ½ ¨\ ¸ Ô ¦ ½ ¨ ¦ ZnCoO\ ¦ q 2 © ô Ç s F K5 Å q s ¸ i ç
) a ZnO \ " f_ © : r y © $ í _ " é ¶ \ @ /K " f H f ¸
´ ú
§ É r 7 H ê ø Ís e [15–26]. t F K t í H Ã ºô Ç ZnCoO\ " f F
& ³$ í e ¦ ¸] X 0 p x ô Ç © : r y © $ í : £ ¤$ í \ @ /ô Ç / B N
)
a õ H f Ð ¦ ÷ &t · ú § ¤ ¦ x . þ j H, ZnO l
ì ø Í Ó ü t| 9 ` ¦ @ / © Ü ¼ Ð ¸Û ¼H { 9 \ " f Û ¼ 2 ;` ¦ f ] X ' a 8
£
¤ ¦ Û ¼ 2 ; & ñ § > =` ¦ ¸] X x 9 ¸ 9 H ½ ¨ ' ÷ &
Fig. 1. Computed values of the Curie temperature T
Cfor various p-type semiconductors containing 5 % of Mn and 3.5 × 10
20holes per cm
3[13].
¦ e Ü ¼ 9, s \ ¦ : x # D h Ðî r Û ¼ 2 ;à Ô Ð_ Û ¼ è Ð" f _
6 £ x6 x 0 p x$ í ` ¦ ¦ > hµ 1 Ï 9 H ½ ¨ > 5 Å q K
"
f r ¸÷ & ¦ e . s H Û ¼ 2 ;à Ô Ð_ Û ¼ èF > hµ 1 Ï\ " f e
#
Q" f_ ZnO l ì ø Í Ó ü t| 9 _ × æ כ ¹$ í ` ¦ ´ ú K º ¡ § õ 1 l x r \ © l
& h Ü ¼ Ð ZnO l ì ø Í èF _ Û ¼ 2 ;à Ô Ð_ Û ¼ 6 £ x6 x \ @ /ô Ç
[ j> ½ ¨ [ þ t _ / B N: x ) a _ | ` ¦ ´ ú K ï r . s Qô Ç
½
¨_ â ì2 £ § \ " f ZnO l ì ø Í_ Ó ü t| 9 ZnCoO_ y © $ í " é ¶
` ¦ & ñ S X > ½ ©" î ¦ Õ ª 6 £ x6 x$ í ` ¦ S X @ / H ½ ¨ H Û
¼ 2 ;à Ô Ð_ Û ¼ è > hµ 1 Ï\ B Ä º × æ כ ¹ . : r ½ ¨\ " f
H ZnCoO \ " f H © : r y © $ í _ : £ ¤$ í _ " é ¶ ` ¦
½
©" î ¦ Ã º è\ _ ô Ç Û ¼ 2 ; & ñ § > = : £ ¤$ í õ s \ ¦ s 6 x ô Ç D h
Ðî r è > hµ 1 Ï\ @ /K ½ ¨ % i . y © $ í _ " é ¶ ` ¦ µ 1 ß y
l 0 AK " f ZnCoO\ " f µ 1 ÏÒ q t H s © õ y © $ í õ _
' a$ í ` ¦ ½ ¨ % i Ü ¼ 9 ZnCoO_ ½ ¨ ¸& h , l F g
< Æ& h : £ ¤$ í 1 p x ª ô Ç Ó ü t o & h : £ ¤$ í \ @ /ô Ç ½ ¨ õ \ ¦ ]
jr % i . 7 H ê ø Ís ÷ & H ZnCoO _ © : r y © $ í : £ ¤$ í s
¸ _ Û ¼ 2 ; ¼ # F g \ _ ô Ç כ s à º è B > h\ _
ô Ç ´ òõ s 9 Co-H-Co 4 ¤ ½ + Ë^ (complex) Ð s À Ò# Q
¸Û ¼H { 9 ` ¦ t H ì r ½ ¨ ¸\ _ K Ä » ¸ H d` ¦ µ 1 ß+ À I [15,22–28]. ¢ ¸ô Ç © $ í : £ ¤$ í _ ZnCoO ¸~ Ã Ì} õ ¸ ì
r µ 1 Ï\ 0 A& h à º è_ Å Ò{ 9 õ Æ ÒØ ¦` ¦ : x ô Ç F & ³$ í e ¦
% i & h Û ¼ 2 ; & ñ § > = : £ ¤$ í ` ¦ Ð ¦ ¦ ] j{ 9 " é ¶ o > í ß , × æ
$ í
í ß ê ø Í, ~ ½ Ó F g x- í ß ê ø Í, HRTEM (High resolution transmission electron microscope) 1 p x _ z ´+ « >õ XPS (x- ray photoelectron spectroscopy), SIMS (secondary ion mass spectroscopy), MCD (magnetic circular dichroism), SQUID (superconducting quantum interference device) 1
p
x _ 8 £ ¤& ñ ` ¦ : x K Ã º è_ 1 l x \ É r Û ¼ 2 ; & ñ § > = : £ ¤$ í ` ¦
½ ¨ % i . : r ½ ¨\ " f ] jî ß H Ã º è\ ¦ : x ô Ç Û ¼ 2 ; & ñ
§ >
=_ ] j# Q ½ ¨ H ª ô Ç Û ¼ 2 ;à Ô Ð_ Û ¼ è > hµ 1 Ï_ 0
p x$ í ` ¦ ] jr 9 Û ¼ 2 ;à Ô Ð_ Û ¼ ½ ¨ ì r _ µ 1 Ï ` ¦ 0 A ô
Ç D h Ðî r > h¥ Æ _ Û ¼ 2 ; ¸] X ~ ½ ÓZ O ` ¦ ] j/ B N ô Ç .
Table 1. The basic physical properties of ZnO [14].
Chemical fomula ZnO
Crystal structure wurtzite structure (P6
3mc) Lattice constants a = 3.25 ˚ Aand c = 5.2 ˚ A
Density 5.606 g/cm
3Hardness Moss hardness 4.6 Melting point 1975
◦C Boiling point 2360
◦C
Band gap 3.3 eV (direct) Refractive index (n
D) 2.0041 Exciton binding energy 60 meV
Carrier concentration <10
6cm
−3Carrier Mobility ∼2000 cm
2/(V·s) at 80 K
II. ZnCoO ; c" e8 ý V R Ë my ¢= k ì Å ô½ Û
ZnO H í ß oÓ ü t s t H î ß & ñ $ í õ 3.3 eV ? /ü @_ V , É r
½ × ¼Ì s \ -t , © : r \ " f 60 meV_ Z } É r " l or : r ½ + Ë \
-t (exciton binding energy), 8 A# Qè ß l F g < Æ (electro- optic) : £ ¤$ í 1 p x B Ä º ª ¦ Ä »6 x ô Ç : £ ¤$ í ` ¦ t ¦ e # Q
"
f [ j@ / ì ø Í ¸^ Ó ü t| 9 Ð l @ /\ ¦ ¸Ü ¼ H Ó ü t| 9 s . ZnO
t ¦ e H l : r Ó ü t o & h : £ ¤$ í ` ¦ ³ ð 1\ & ñ o % i .
ZnO _ 8 A# Qè ß F g < Æ& h © & h ` ¦ Ö ¸6 x " f Co, Mn, Fe 1
p
x` ¦ ¸i ç # $ í ì ø Í ¸^ \ ¦ > hµ 1 Ï 9 H ¸§ 4 s 2000¸
@
/\ ] X # Q[ þ t " f / å L5 Å q ¸ Ð ' ÷ &% 3 . : £ ¤ y , s Qô Ç s
F K5 Å q s ¸i ç ) a ZnO \ " f © : r y © $ í s 0 p x ½ + É כ s
H s : r& h \ V8 £ ¤ õ < Êa z ´+ « >& h õ ü < n s Û ¼_ > h µ
1 Ï 1 p x, ª ô Ç ½ ¨ õ µ 1 ϳ ð÷ & ¦ e . ] j { 9 " é ¶ o > í
ß ` ¦ : x K " f s : r& h Ü ¼ Ð ZnO? /\ V, Cr, Fe, Co, Ni 1 p x _
s F K5 Å q s u ¨ 8 | ¨ c â Ä º y © $ í s Ä » ¸ | ¨ c à º e Ü ¼ 9 Ti, Cu 1 p x É r © $ í : £ ¤$ í ` ¦ | 9 כ s H ½ ¨ õ
µ
1 ϳ ð ) a s Ê ê, © : r y © $ í ì ø Í ¸^ Ó ü t| 9 õ y © $ í " é ¶ \
@
/ô Ç ½ ¨ Ö ¸ µ 1 Ïy ' ÷ &% 3 [17]. s Qô Ç Ó ü t| 9 [ þ t × æ
\
ZnO\ Sc [29,30], Ti [29], V [22,32,33], Cr [16,29,34, 35], Mn [36–44], Fe [45, 46], Co [7, 15–29, 35–45, 47–52], Ni [46–53] ü < Cu [54–58] 1 p x s ¸i ç ) a â Ä º\ y © $ í s
è ß H z ´+ « >& h ½ ¨ õ Ð ¦÷ &% 3 [59]. t ë
ß s Qô Ç @ /Â Òì r _ Ó ü t| 9 [ þ t É r © : r Ð B Ä º ± ú É r : r ¸ _
Tc\ ¦ ? /% 3 ` ¦ ÷ r ë ß m © : r y © $ í s Ð ¦ ) a ZnCoO, ZnMnO, ZnVO 1 p x \ " f H y © $ í ÷ r ë ß m ©
$ í , ì ø Íy © $ í 1 p x _ l & h : £ ¤$ í s ½ ¨ _ r « Ñ ] j
~
½ ÓZ O õ 8 £ ¤& ñ ~ ½ ÓZ O \ " f Ð © s > Ð ¦ ÷ &% 3 .
s
× æ \ " f ¸ © : r y © $ í : £ ¤$ í ` ¦ Ðs H @ /³ ð& h V , É r {
ì ø Í ¸^ Ó ü t| 9 Ð" f ZnCoO ~ à Ì} õ ¸ì r ´ ú \ " f y ©
$ í
µ 1 Ï & ³ " é ¶ \ @ /ô Ç ª ô Ç s : r& h , z ´+ « >& h ½ ¨ õ
| 9 × æ& h Ü ¼ Ð Ð ¦÷ &% 3 . t ë ß t F K t ¸ ZnCoO _
© : r y © $ í " é ¶ \ @ /K " f H ´ ú § É r s | õ " f Ð ¸í H
Table 2. The reported magnetic properties and T
cof Co doped ZnO thin films [59].
Fabrication Co concentration T
c[
◦C] magnetic Ref.
method (at.%) properties
Sol-gel coating 5 >300 0.5 µ
B/Co [60]
MOCVD 35 >300 0.1 µ
B/Co [37]
UA-CVD 2 >300 0.4 µ
B/Co [61]
UA CVD 2 >300 0.8 µ
B/Co [41]
PLD 5 (5-25) >280 0.01 µ
B/Co [16]
PLD 25 - spin glass [50]
PLD 5 >300 0.7 µ
B/Co [43]
PLD 25 >300 1.0 µ
B/Co [62]
PLD 10 >300 10
−5µ
B/Co [51]
PLD 5 >300 2.6 µ
B/Co [29]
PLD 5 >300 1.04 µ
B/Co [42]
PLD 3(1-25) >300 5.9 µ
B/Co [63]
PLD 10 - AF [64]
rf-sputter 3.5 (3.5-11.5) >350 0.21 µ
B/Co [65]
rf-sputter 7 (7-17) >300 0.06 µ
B/Co [66]
rf-sputter 25 300 0.8 µ
B/Co [48]
rf-sputter 4 >790 6.1 µ
B/Co [47]
rf-sputter 12 (8-31) >300 0.04 µ
B/Co [67]
PAMBE 0.3-0.5 >300 3 µ
B/Co [68]
Laser MBE 5 >300 1.5 µ
B/Co [36]
÷
& H õ [ þ t s Ð ¦÷ & ¦ e . ³ ð 2 H t F K t µ 1 ϳ ð ) a ZnCoO $ í ì ø Í ¸^ ½ ¨ 7 Hë H[ þ t \ " f r « Ñ_ ] j ~ ½ ÓZ O õ 8
£ ¤& ñ ) a l & h : £ ¤$ í ` ¦ כ ¹ # Ð# ï r . @ /Â Òì r _ 7 H ë
H[ þ t \ " f y © $ í : £ ¤$ í s © : r s © t t 5 Å q ÷ &% 3 t ë ß , Co s : r { © $ í _ ß ¼l H 10
−5µ
B\ " f Ò' 6.1 µ
Bt
ª > Ð ¦ ÷ & ¦e . : £ ¤ y , sol-gel Z O Ü ¼ Ð ] j ¸ ) a r
« Ñ_ â Ä º l & h : £ ¤$ í s r « Ñ_ \ P % o : r ¸\ y ©
>
_ > r % i Ü ¼ 9, É r 7 £ x à ÌZ O Ü ¼ Ð ] j ¸ ) a r « Ñ H Û ¼ 2 ; /
å
J A Û ¼ ¢ ¸ H © $ í , ì ø Íy © $ í 1 p x ª ô Ç : £ ¤$ í s Ð ¦÷ &
%
3 . t ë ß t F K t ZnCoO\ " f F & ³$ í õ ¸] X 0 p x ô
Ç y © $ í : £ ¤$ í \ @ /ô Ç / B N ) a õ H f Ð ¦÷ &t · ú §
¤ ¦ x .
III. < g ºU ê s0 n É; c  \ ¥ T V ê s º ì Å
1. V ê s Æ X ØP ê s V R Ë ¤V R ËÊ Ý T V ê s
· ú
¡" f l Õ ü t ô Ç כ õ ° ú s ZnCoO\ @ /ô Ç y © $ í : £ ¤$ í É r
´ ú
§ É r ½ ¨ ü < ª ô Ç z ´+ « >~ ½ ÓZ O 1 p x Ü ¼ Ð | 9 × æ& h Ü ¼ Ð
½
¨÷ &% 3 . t ë ß ½ ¨ ü < z ´+ « > ~ ½ ÓZ O \ l & h : £ ¤
$ í
s " f Ð { 9 u t · ú § ¤ ¦ ´ ú § É r 7 H ê ø Ís t F K ¸ > 5 Å q ÷ &
¦ e . s H @ /Â Òì r r « Ñ_ ] j õ & ñ \ " f µ 1 ÏÒ q t H Co
'
aº s © _ Ò q t$ í M :ë H Ü ¼ Ð # . : £ ¤ y , ZnO
?
/\ " f ¸i ç ) a s F K5 Å q s Zn 0 Au \ ¦ u ¨ 8 t 3 l w ¦,
Co-F K5 Å q < Ê É r Co í ß oÓ ü t © ` ¦ + þ A$ í < Ê\ Ó ü É r 0 l x ¸
Ð > r F H s F K5 Å q _ Û ¼ 2 ; B > h\ _ K " f y © $ í s Ä
» ¸ ÷ & H כ s m , ¸ < Ê É r s ß ¼ Ð Û ¼H { 9 _ s
© \ _ K y © $ í s l M :ë H s . ¢ ¸ô Ç, @ /Â Ò ì
r y © $ í ` ¦ 8 £ ¤& ñ H ~ ½ ÓZ O Ü ¼ Ð SQUID (superconduct- ing quantum interference device) < Ê É r VSM (vibrating sample magnetometer) 1 p x õ ° ú s ü @Â Ò_ l © \ É r r
« Ñ_ $ í o\ ¦ 8 £ ¤& ñ H magnetometry\ ¦ 6 x
>
÷ & ¦ s \ ¦ : x K " f H r « Ñ? /\ > r F H s © Ü ¼ Ð Â
Ò' H y © $ í ` ¦ & ñ S X > ½ ©" î ½ + É Ã º \ O l M :ë H s
[69]. Õ ª QÙ ¼ Ð © : r y © $ í : £ ¤$ í ` ¦ 8 £ ¤& ñ ¦ " é ¶
`
¦ µ 1 ßy l 0 AK " f H r « Ñ\ > r F H s © ` ¦ ] j
H כ s Õ ª Ø ¦ µ 1 Ï& h s ) a . : r ½ ¨\ " f H sol-gelZ O õ rf- sputterZ O 1 p x` ¦ s 6 x # ¸~ Ã Ì} õ ¸ ì r ´ ú ` ¦ ] j
¦ ] j ~ ½ ÓZ O õ ¸| \ É r ½ ¨ ¸& h , l & h , l & h :
£ ¤$ í _ o\ ¦ ½ ¨ % i .
2. Sol-gel 0 n É® z º < gX c lc Ü R ZnCoO
1) Co ¸i ç | ¾ Ó\ É r precipitation
Sol-gel Z O É r F K5 Å q í ß oÓ ü t` ¦ ] j ½ + ÉÃ º e H ~ ½ ÓZ O × æ _
Ð+ ¸ { 9 ÷ r ë ß m Û ¼ 2 ; ïh A ~ ½ ÓZ O ` ¦ 6 x
# ~ Ã Ì} ` ¦ ] j ½ + É Ã º e . É r ~ ½ ÓZ O \ q K ¸i ç ÷ &
H " é ¶ è_ q Ö ¦` ¦ q §& h ~ 1 ¦ & ñ S X > ¸] X ½ + É Ã º e H s
& h s e . : r ½ ¨\ " f H sol-gel Z O õ Û ¼ 2 ; ïh A ~ ½ ÓZ O
`
¦ 6 x # Co 10 mol% ¸i ç ) a ZnCoO\ ¦ ¸~ Ã Ì} Ü
¼ Ð ] j % i . r Ó ü t| 9 Ð Zinc accetate dihhydrate (Zn(CH
3COOH)
2·2H
2O) ü < cobalt acetate tetrahydrate (Co(CH
3COOH)
2·4H
2O)\ ¦ 6 x # Co_ ¸i ç 0 l x ¸ (0, 0.5, 0.7, 1, 5, 7, 10, 15, 20 mol%) _ sol-gel 6 xÓ o` ¦ ] j
¦ s # Q (0001) l ó ø Í 0 A\ 200 - 250 nm ¿ ºa _
~ Ã
Ì} ` ¦ ] j % i . Û ¼ 2 ; ïh A ) a ~ Ã Ì} É r O
2ì r 0 Al , 700
◦
C \ " f 1ì r & ñ ¸ Ä »t 9 & ñ o % i .
Õ
ªa Ë > 2 H sol-gel õ Û ¼ 2 ; ïh AZ O Ü ¼ Ð ] j ) a ~ Ã Ì} _
: r ¸\ É r y © $ í _ o (M-T curve) (Õ ªa Ë > 2(a))ü <
SQUID Ð 8 £ ¤& ñ ) a © : r \ " f_ s § 4 / B G (M-H curve) (Õ ª a Ë
> 2(b))` ¦ · p . M-T / B G \ " f : r ¸\ É r l ¸ F '
pà Ô_ o H ^ & h Ü ¼ Ð © $ í _ o â ¾ Óõ Ä » ô
Ç + þ AI \ ¦ · p . t ë ß © : r t y © $ í & h : £ ¤$ í s
¦ Co_ ¸i ç | ¾ Ó_ 7 £ x \ & h y © $ í s 7 £ x
H כ ` ¦ · ú à º e . ¢ ¸ô Ç © : r Â Ò H t y © $ í ©
s H ' a8 £ ¤ ÷ &t · ú § ¤ . Õ ªa Ë > 2(b)\ e H M-H /
B G \ " f ¸ Ì º§  ô Ç y © $ í s § 4 / B G ` ¦ S X ½ + É Ã º e Ü ¼ 9 Co_ ¸i ç 0 l x ¸ 7 £ x ½ + Éà º2 ¤ 8¹ ¡ ¤ 8 Ì º§  ô Ç y © $ í
Fig. 2. (a) Temperature dependence of magnetization in 500 Oe and (b) hysteresis curves measured at 350 K for Co-doped ZnO film [15].
:
£ ¤$ í ` ¦ · p . X- r] X 8 £ ¤& ñ \ " f H Co _ ¸i ç 0 l x
¸ 20 mol% s { 9 M :\ H Co F K5 Å q 1 p x` ¦ q 2 © ô Ç s
© s ' a8 £ ¤ ÷ &t · ú § ¤ ¦ 25 mol% { 9 M :\ H x- r] X © \
"
f Ì º§  ô Ç s © s Ò q t$ í ÷ &% 3 . t ë ß { 9 ì ø Í& h x-
r] X 8 £ ¤& ñ É r Õ ª ] jô Ç ) a ì r K 0 p x Ü ¼ Ð K ¸ s Ý ¼_ s
© ` ¦ ¢ - a# 4 > 8 £ ¤& ñ t 3 l w ½ + É Ã º e .
Sol-gel Z O Ü ¼ Ð ] j ) a ZnCoO _ y © $ í _ " é ¶ ` ¦ ½ ©
"
î l 0 A # ZnCoO ¸ì r ´ ú \ @ /K × æ$ í r] X z ´ +
«
>` ¦ à º' % i . Õ ªa Ë > 3 É r sol-gel Z O \ " f ZnCoO ì r ´ ú _ Co _ ¸i ç | ¾ Ós 5, 10, 15, 30 mol% ZnCoO ¸ì r ´ ú \
@
/ô Ç × æ$ í r] X 8 £ ¤& ñ õ Rietveld Z O Ü ¼ Ð refinementô Ç
õ s . ¸ H refinement ) a õ H ZnO, CoO, Co
3O
4, Co-metal 1 p x _ ½ ¨ ¸\ ¦ 6 x K reliable factor (R-factor) 2.8% s Ð, z ´] j 8 £ ¤& ñ ) a r] X J õ B Ä º ¸ ú { 9 u
%
i . Co 5 mol% { 9 M :\ H × æ$ í r] X © \ " f í H Ã ºô Ç ZnO © ë ß s ' a8 £ ¤ ÷ &% 3 (Õ ªa Ë > 3(a)). 7 £ ¤ ¸i ç ) a Co H
¸¿ º ZnO ? /\ " f Zn o \ ¦ u ¨ 8 K [ þ t # Q" f D h
Ðî r s © ` ¦ Ò q t$ í r v t · ú § H . Znü < Co_ Ä » ô Ç s
: r ì ø Í â Ü ¼ Ð K ½ ¨ ¸& h + 'd ¦a Ë > 1 p x s ß ¼> { 9 # Q t
· ú
§ ¦ ZnO \ ¦ Õ ª@ / Ð Ä »t < Ê` ¦ · ú Ã º e . t ë ß Co ¸i ç | ¾ Ós 10, 15 mol%{ 9 M :\ H í H Ã ºô Ç ZnO ë ß Ü ¼
Ð H & ñ S X > × æ$ í r] X J s refinement ÷ &t · ú §
Fig. 3. Neutron diffraction data and results of refine- ment: P1, P2, P3 and P4 correspond to the ZnO, Co
3O
4, CoO, and Co metallic phase, respectively. The dotted, solid line and vertical bar represent the observed value, calculated value, and the Bragg position, respectively.
The solid line on the bottom of the figure is applicable to the difference between the observed and calculated value. (a) Co 5 mol%-doped ZnO has a single phase.
(b), (c), and (d) show Co 10, 20, and 30 mol%-doped ZnO, respectively [24].
¤Ü ¼ 9 Co
3O
4 © s l r % i . s Qô Ç â ¾ Ó
É r Co _ ¸i ç | ¾ Ós 20 mol% { 9 M : t t 5 Å q ÷ &% 3 . (Õ ª a Ë
> 3(b), 3(c)) Õ ªo ¦ Co_ ¸i ç | ¾ Ós 30 mol% { 9 M :\
H Co
3O
4 © ü @\ CoO (P3) ü < Co-metal (P4) © s 8 £ ¤& ñ
÷
&% 3 (Õ ªa Ë > 3 (d)). s Qô Ç o â ¾ Ó É r Õ ªa Ë > 4\
· p כ % ! 3 54
◦ü < 96
◦Â Ò H _ r] X J _ o Ð 8 F G
"
î > è ß . Õ ªa Ë > 4 H Co _ ¸i ç | ¾ Ó 5, 10, 15, 20, 30 mol% \ " f_ o\ ¦ [ j > Ð# ï r . Co ¸i ç
÷
&t · ú § É r ZnO â Ä º 54.4
◦\ " f r] X i s ' a8 £ ¤ ÷ &t · ú §
H . Õ ªa Ë > 4(a)\ " f Ð H ü < ° ú s 5 mol% s \ " f H Co Zn o \ ¸ ú u ¨ 8 K [ þ t # Q" f Co\ _ ô Ç D h Ðî r i
s t · ú § H . Õ ª Q Co_ 0 l x ¸ 10 mol% s
© \ " f 54.4
◦\ " f D h Ðî r i s z ¤Ü ¼ 9 0 l x ¸ 7 £ x
½
+ ÉÃ º2 ¤ Co \ _ ô Ç D h Ðî r ½ ¨ ¸_ © s & h & h 7 £ x < Ê` ¦ · ú Ã
º e . Õ ªo ¦ Õ ªa Ë > 4(f)-(j)\ " fü < ° ú s 96.1
◦\ " f
H r] X i É r ZnO (202) \ K { © ô Ç . ¸i ç 0 l x ¸
7
£
x ½ + ÉÃ º2 ¤ ZnO (202) i _ [ jl y è ¦ D h Ðî r i s
94.5
◦ü < 96.1
◦\ è ß .
p
[ jô Ç s © _ > r F \ ¦ 7 á § 8 & ñ S X y 7 £ x l 0 AK
~
½ Ó F g x- ` ¦ s 6 x # EXAFS (extended x-ray fine structure) ü < XANES(x-ray absorption near edge struc- ture) 1 p x _ z ´+ « >` ¦ ' % i [15,24–27]. Õ ªa Ë > 5 H sol- gel Z O õ Û ¼ 2 ;- ïh AÜ ¼ Ð ] j ) a ~ Ã Ì} \ @ /K " f í ½ Ó 5
Å
q l ½ ¨ è_ ~ ½ Ó F g (synchrotron-light)` ¦ 6 x ô Ç EX- AFS 8 £ ¤& ñ \ " f % 3 # Q Coü < Zn K-edge[ þ t Ð Â Ò' % 3 # Q
Fig. 4. Neutron diffraction peaks near 52
◦and 96
◦de- pending the Co doping concentration [24].
z
´½ ¨ ¸ < ÊÃ º (radial structure function, RSF)\ ¦ · p .
Õ
ªa Ë > 5\ H Co F K5 Å q, CoO, Co
3O
4Õ ªo ¦ ZnO 1 p x _ l ï
r r « Ñ_ õ ü < q § # ? /% 3 (Õ ªa Ë > 5(a)-(d)).
õ \ " f Co 5 mol% ¸i ç ) a RSF H Õ ª + þ AI ü < 0 Au \ e
# Q" f í H Ã ºô Ç ZnO_ õ ü < ¸ ú { 9 u ô Ç . Õ ªa Ë >\ H ³ ð r
÷ &t · ú § ¤t ë ß Fourier-transform ) a imaginary  Òì r ¸ B
Ä º ¸ ú { 9 u K " f 5 mol% s \ " f H Co " é ¶ Zn o
\ ¸ ú u ¨ 8 K [ þ t # Qy ` ¦ · ú Ã º e % 3 . Õ ª Q Co_ ¸ i ç
0 l x ¸ 7 £ x ) a 20 mol%{ 9 M :\ H 2 ∼ 3 ˚ A \ " f ´ ú § É r
o { 9 # Q ¦ s H Co
3O
4_ 1 l x õ { 9 u ô Ç . 0.5 ∼ 1.8 ˚ A \ " f_ o H Co-O \ K { © 9 20 mol%\ " f H
o \ O . 30 mol%{ 9 M :\ H É r © _ l # H × ¦ ¦ Co-F K5 Å q © _ l # ß ¼> H כ Ü ¼ Ð 8 £ ¤& ñ ÷ &% 3 .
s
Qô Ç õ [ þ t ÐÂ Ò' sol-gel Z O Ü ¼ Ð ] j ) a ~ Ã Ì} _ â Ä º 700
◦C \ P % o \ " f µ 1 ÏÒ q tô Ç Co ' aº precipitation É r y ©
$ í
` ¦ ? / H s © ` ¦ Ò q t$ í > ÷ & ¦ s Qô Ç s © s
© : r y © $ í \ l # ¦ e H כ ` ¦ · ú Ã º e .
2) \ P % o : r ¸\ É r precipitation
{ 9
ì ø Í& h Ü ¼ Ð s © s Ò q t$ í ÷ & H " é ¶ É r ¸i ç " é ¶ _ solubility limit s © _ ¸i ç ü @\ ¸ ´ ú § É r É r z ´+ « > ¸|
\
_ > r ô Ç . ZnCoO\ " f µ 1 ÏÒ q t H s © _ ¸] X ` ¦ 0 A K
" f s © _ Ò q t$ í ¸| õ Co " é ¶ _ solubility limit` ¦ 8
£ ¤& ñ H כ É r B Ä º × æ כ ¹ . ¦ : r \ " f_ \ P % o \ ¦ : x ô
Ç s © _ Ò q t$ í ` ¦ % 3 ] j ¦ ZnCoO Ó ü t| 9 _ y © $ í _
"
é
¶ ` ¦ ½ ©" î l 0 AK l > r _ \ P % o : r ¸\ ¦ ± ú Æ Ò# Q ª
| 9
_ ¸ì r ´ ú õ ~ à Ì} r « Ñ\ ¦ S X Ð % i . ¦ : r \ " f_
\ P
% o õ & ñ É r Co precipitation` ¦ Ä » ¸ # Co ' aº s
© ` ¦ ~ 1 > Ò q t$ í r ~ ´ Ã º e . Õ ªa Ë > 6 É r sol-gelZ O Ü ¼ Ð
Fig. 5. Co K-edge EXAFS results of the Co reference and several Co-containing specimens: they are EXAFS signals for Co K-edge of (a) Co-metal reference, (b) CoO reference, (c) Co
3O
4reference, (e) Co (5 mol%)- doped ZnO, (f) Co (20 mol%)-doped ZnO, and (g) Co(30 mol%)-doped ZnO. (d) The Zn K-edge EXAFS signal of pure ZnO was added [24].
]
j ) a Zn
0.9Co
0.1O ¸ì r ´ ú r « Ñ\ " f \ P % o : r ¸ ¸
|
\ É r s © _ Ò q t$ í ` ¦ x- r] X õ \ P ì r$ 3 õ \ ¦
· p . Õ ªa Ë > 6(a)\ " f ZnCoO ¸ì r ´ ú _ Á º> < Hz ´ (weight loss) õ differential thermal analysis (DTA) 8 £ ¤& ñ
õ \ ¦ · p . s õ \ " f · ú Ã º e 1 p w s r « Ñ ½ + Ë$ í s
Ê ê z e H ï ß > r Ä »l Ó ü t[ þ t É r 300
◦C s \ " f @ /Â Ò ì
r ] j ÷ & H כ ` ¦ · ú Ã º e . Õ ªa Ë > 6(b) \ " f H 300
◦C ü
< 500
◦C \ " f_ \ P % o \ s © _ Ò q t$ í s ² ú t
H כ ` ¦ S X ½ + É Ã º e . 300
◦C \ " f \ P % o ) a â Ä º ZnCoO & ñ $ í s ì r" î y z ¤t ë ß s © \ @ /ô Ç x-
r] X J É r > r F t · ú § H . t ë ß 1 l x{ 9 ô Ç ZnCoO
¸ì r ´ ú r « Ñ\ @ /K " f 500
◦C \ " f \ P % o ÷ &% 3 ` ¦ â Ä
º Co
3O
4 © s > r F < Ê` ¦ · ú Ã º e . Õ ª QÙ ¼ Ð 500
◦C s
© _ ¦ : r \ P % o H ~ 1 > Co ' aº s © ` ¦ Ò q t$ í t ë
ß 300
◦C \ " f H s © s Ò q t$ í ÷ &t · ú § H . s Qô Ç õ
H sol-gel Z O Ü ¼ Ð ] j ¸ ) a ¸ì r ´ ú \ ë ß K { © H כ s
m Û ¼ 2 ; ïh Aõ rf-sputtering Z O Ü ¼ Ð ] j ) a ~ Ã Ì} r
«
Ñ\ ¸ ð ø Ít Ð & h 6 x ÷ &% 3 . 7 £ ¤, 500
◦C s © \ " f_
¦ : r \ P % o H Co- ' aº s © ` ¦ Ò q t$ í ¦ extrinsicô Ç y
© $ í _ l # H " é ¶ s ) a .
Fig. 6. (a) The weight loss and differential thermal anal- ysis of Zn
0.9Co
0.1O precursor powder. (b) XRD patterns of Zn
0.9Co
0.1O annealed under various conditions. The marked peaks with arrows correspond to Co
3O
4phase [27].
0
A_ õ \ " f sol-gelZ O Ü ¼ Ð ] j ) a ~ Ã Ì} É r SQUID 8 £ ¤
&
ñ ` ¦ : x K $ : r  Ò' © : r s © t Ì º§  ô Ç y © $ í : £ ¤$ í
`
¦ ? / 9 # Q* ô Ç y © $ í © s _ 1 l x` ¦ Ðs t · ú §
¤ . t ë ß ZnCoO ¸ì r ´ ú r « Ñü < ¸~ à Ì} r « Ñ\
H Co F K5 Å q, Co
3O
4, CoO 1 p x _ s © s > r F ¦ e Ü ¼ Ù
¼ Ð 8 £ ¤& ñ ) a y © $ í : £ ¤$ í \ " f s © _ y © $ í _ l #
\
¦ ¢ - a y C ] j½ + É Ã º \ O . ¸i ç 0 l x ¸ü < \ P % o : r ¸\
É
r ½ ¨ ¸ ½ ¨\ " f ZnCoO\ Ò q t$ í ÷ & H s © É r Co _ ¸ i ç
0 l x ¸ 20 mol% s © ÷ & \ P % o : r ¸ 500
◦C s
© | ¨ c M : µ 1 ÏÒ q t H כ Ü ¼ Ð µ 1 ß) & . r « Ñ ] j × æ \ µ 1 Ï Ò q
t H s © É r ZnCoO \ ü @Â Ò& h (extrinsic) y © $ í ` ¦ ]
j/ B N < ÊÜ ¼ Ð+ y © $ í " é ¶ ½ ©" î \ ´ ú § É r D ¥ ê ø Íõ # Q 9¹ ¡ §` ¦ ]
j/ B N ô Ç . Õ ª QÙ ¼ Ð $ í ì ø Í ¸^ ½ ¨\ " f SQUID 8 £ ¤& ñ
`
¦ : x K Ì º§  ô Ç y © $ í s § 4 / B G ` ¦ 8 £ ¤& ñ % i 8
¸ ¦Ä »ô Ç(intrinsic) ZnCoO © : r y © $ í : £ ¤$ í e ` ¦ ½ ©& ñ
½
+ É Ã º \ O . t ë ß Co 5 mol%{ 9 M :\ H × æ$ í ü <
É
r # Q z ´+ « >\ " f s © s t · ú §6 £ § \ ¸ Ô ¦ ½ ¨
¦ # y ô Ç y © $ í : £ ¤$ í ` ¦ ? / 9 s H 6 £ § © \
"
f [ O " î xt ë ß sol-gel ~ Ã Ì} ] j / B N& ñ × æ \ > r F H Ã
º è\ _ ô Ç l # Ð è ß . Sol-gel Z O õ H ² ú o ~ Ã Ì} ]
j r \ Ã º è Ä »{ 9 | ¨ c 0 p x$ í s & h É r sputtering ~ ½ ÓZ O Ü
¼ Ð ] j ) a ZnCoO ~ Ã Ì} _ õ ü < q § < ÊÜ ¼ Ð+ Ã º è _
´ òõ \ ¦ 7 á § 8 " î S X > Ð# ï r .
Fig. 7. (a) HRXRD patterns of Co-doped ZnO with dif- ferent Co concentrations (black arrow: Co
3O
4secondary phase). (b) FWHM of the (002) peak and lattice con- stant of the c-axis. (c) Azimuthal φ-scan of (101) peaks for different Co concentrations in Co-doped ZnO [70].
3. RF-sputtering 0 n É® z º < g ºc Ü R ZnCoO
s # Q(0001) l ó ø Í0 A\ Zn
1−xCo
xO (x = 0, 0.05, 0.1, 0.2, 0.4) ~ à Ì} ` ¦ rf-sputter ~ ½ ÓZ O ` ¦ 6 x # 7 £ x à Ì
%
i . l : r / B N ¸ H 1.6 × 10
−6Torr % i ¦ Ar (∼99.999
%) l ^ \ ¦ 6 x # 5 mTorr, 350
◦C \ " f 7 £ x à Ì` ¦ % i Ü
¼ 9 rf-power H 40 W % i . $ í © : r ¸ü < e ¦ Ý ¼ 0
> H Co F K5 Å q _ 9 þ t QÛ ¼' a A` ¦ ] jô Ç l 0 AK ' ½ ¨
\
¦ : x K þ j@ /ô Ç ± ú > [ O & ñ % i . 7 £ x Ã Ì ) a ~ à Ì} _ $ í ì r É r GDS (glow discharge spectroscopy) 8 £ ¤& ñ ` ¦ : x K S X
% i .
Õ
ªa Ë > 7 É r rf-sputtering Z O Ü ¼ Ð ] j ) a ZnCoO ~ Ã Ì} _
¦ì r K 0 p x x- r] X õ \ ¦ Ð# ï r . $ í © ) a ¸ H ~ à Ì}
É r c-» ¡ ¤ ~ ½ Ó ¾ ÓÜ ¼ Ð B Ä º ¸ ú $ í © ÷ &% 3 Ü ¼ 9 Õ ªa Ë > 7(a)\ " f ^ ¦ Ã
º e 1 p w s Co 20 mol% s { 9 M :\ H (002) ü < (004)
\
K { © H r] X peakë ß 8 £ ¤& ñ ÷ &% 3 . t ë ß ¸i ç 0 l x ¸
30 mol% Ð 7 £ x 31.20
◦ü < 36.84
◦\ " f Co
3O
4\ K
{ © H r] X x ß ¼ z ¤ . Õ ªa Ë > 7(b) H Co ¸i ç 0 l x
¸\ É r c-» ¡ ¤ © à ºü < (002) \ K { © H peak _ ì
ø Íg Ë :; ¤ _ o\ ¦ · p . Co_ 0 l x ¸ 7 £ x < Ê\
Zn
2+_ s : r ì ø Í â (∼74.0 pm)õ Co
2+_ s : r ì ø Í â (∼74.5 pm) _ s \ " f l H _ strain\ _ K 7
£
x ô Ç . t ë ß , 30 mol% s Ê ê\ H Co ü < ' aº ô Ç s
© s Ò q t$ í H d \ y è H כ Ü ¼ Ð z ¤ . Õ ª a Ë
> 7(c) H ¹ ¢ ¤$ í ) a Zn
0.8Co
0.2O r « Ñ_ x- φ-scan\ " f (101) _ 6-fold @ /g A` ¦ ¸ ú Ð# ï r . s Qô Ç õ H rf- sputter Ð ] j ) a ~ Ã Ì} \ " f Co H 20 mol% t u ¨ 8
½
+ É Ã º e 6 £ §` ¦ ´ ú K ï r .
Fig. 8. Co 2p
3/2and Co 2p
1/2peaks of the XPS spectra for different Co concentrations [70].
Õ
ªa Ë > 8 É r Co ¸i ç 0 l x ¸\ É r Co s : r _ XPS Û ¼& 7 à Ô
_ o\ ¦ Ð# ï r . Õ ªa Ë >\ ³ ðr ) a P
2(780.2 eV) ü <
P
5(795.7 eV) H Zn o \ u ¨ 8 ô Ç Co s : r _ Co 2p
3/2ü <
Co 2p
1/2\ y y K { © ô Ç . s H 20 mol% _ ¸i ç 0 l x ¸ t
Co ZnO\ ¸ ú u ¨ 8 K [ þ t # Qy ` ¦ ´ ú ô Ç . ¢ ¸ô Ç ¿ º \
-t _ s H 15.5 eV Ð" f ZnCoO\ @ /K " f Ð ¦ ) a
É
r õ ü < ¸ ¸ ú { 9 u ô Ç . P
3(785.7 eV) ü < P
5(801.8 eV)
H P
2ü < P
2_ shake-up 0 A$ í x ß ¼s . t ë ß Co 40 mol% { 9 M :\ H P
1(777.7 eV) and P
4(792.7. eV) \ " f
½ + Ë\ -t 8 £ ¤' õ A÷ &% 3 . s H Co F K5 Å q Co 2p
3/2õ Co 2p
1/2\ K { © ) a . ¢ ¸ô Ç Hall 8 £ ¤& ñ \ " f 0 l x ¸ 10
2C
& ñ ¸ 7 £ x % i . s Qô Ç õ H Co F K5 Å q © s © { © Â Ò ì
r > r F l M :ë H s .
Õ
ªa Ë > 9 H Co ¸i ç 0 l x ¸\ É r F g < Æ& h È Òõ ¸ (Õ ªa Ë >
9(a)) ü < MCD (Õ ªa Ë > 9(b))_ Û ¼& 7 à Ô _ o\ ¦
· p . Õ ªa Ë >\ " f 20 mol%_ Co ¸i ç 0 l x ¸ s \ " f H T
1(2.18 eV), T
2(2.01 eV), Õ ªo ¦ T
3(1.87 eV) \ " f_ F g < Æ
&
h s > r F 9, s H Zn o \ u ¨ 8 ô Ç Co_ d-
C ¸ ç ß _ s \ K { © ô Ç . s Qô Ç õ H Co
2+ZnO ½ ¨ ¸\ " f Zn o \ ¸ ú u ¨ 8 Ù þ ¡6 £ §` ¦ Ð# ï r .
t ë ß 40 mol% s © { 9 â Ä º H Co F K5 Å q © s @ /Â Òì r + þ A
$ í
÷ &# Q s Qô Ç i ` ¦ ^ ¦ Ã º \ O Ü ¼ 9 F g < Æ& h È Òõ ¸ ß ¼
>
y èÙ þ ¡6 £ §` ¦ Ð# ï r . s õ H rf-sputteringZ O Ü ¼ Ð
~ Ã
Ì} s ] j ¸÷ &% 3 ` ¦ â Ä º, Co_ ¸i ç 0 l x ¸ 20 mol% t
H Co s : r s Zn o \ ¸ ú u ¨ 8 9 Co clusteringõ Co í ß oÓ ü t 1 p x _ s © _ Ò q t$ í É r { 9 # Q t · ú § ¦ Al
2O
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![Table 2. The reported magnetic properties and T c of Co doped ZnO thin films [59].](https://thumb-ap.123doks.com/thumbv2/123dokinfo/5433022.231881/4.892.66.433.189.388/table-reported-magnetic-properties-t-doped-zno-films.webp)
![Fig. 4. Neutron diffraction peaks near 52 ◦ and 96 ◦ de- de-pending the Co doping concentration [24].](https://thumb-ap.123doks.com/thumbv2/123dokinfo/5433022.231881/6.892.71.423.157.401/fig-neutron-diffraction-peaks-near-pending-doping-concentration.webp)
![Fig. 8. Co 2p 3/2 and Co 2p 1/2 peaks of the XPS spectra for different Co concentrations [70].](https://thumb-ap.123doks.com/thumbv2/123dokinfo/5433022.231881/8.892.73.425.161.409/fig-p-p-peaks-xps-spectra-different-concentrations.webp)
![Fig. 17. The changes of carrier concentration (n) and re- re-sistivity (ρ) by hydrogen injection and ejection process, determined by Hall effect measurement at room temper-ature [28]](https://thumb-ap.123doks.com/thumbv2/123dokinfo/5433022.231881/13.892.466.826.157.517/changes-concentration-sistivity-hydrogen-injection-ejection-determined-measurement.webp)
