½ ¨ 7 Hë H Sae Mulli (The Korean Physical Society), Volume 48, Number 2, 2004¸ 2 Z 4, pp. 170∼173
Cu(110) » ì Å; c Ar + T Æ X Ø8 ý û s Þô v Ú ÇÊ Ý
» ç ¡g ` @ ∗ · ø ¶ B* × <
$ í
ç H ' a @ / < Æ § Ó ü t o < Æõ , Ã º" é ¶ 440-746
L. D. Sun
Department of Physics, Linz University, Austria, A-4040 (2003¸ 12 Z 4 30{ 9 ~ Ã Î6 £ §)
Cu(110) ³ ð \ Ar
+s : rØ æ[ t õ annealing õ & ñ ` ¦ RDS(Reflectance Difference Spectroscopy) ü <
STM(Scanning Tunneling Microscopy)` ¦ 6 x # ½ ¨ % i . 350 Kü < 45 K\ " f Cu(110) ³ ð \ Ar
+s : rØ æ[ t É r | _ Û ¼ü < É r cluster\ ¦ ³ ð \ + þ A$ í ô Ç . s : rØ æ[ t 1 l xî ß \ 2.1 eV 4 x Ä ºo H ¢ - a
y è F g(quench) ÷ & ¦, 4.38 eV 4 x Ä ºo H Z } É r \ -t A á ¤ Ü ¼ Ð s 1 l xô Ç . s s 1 l x É r subsurface t
%
i \ + þ A$ í ) a vacancy_ 0 l x ¸ü < ' aº s e . Annealing 1 l xî ß \ , 2.1 eV 4 x Ä ºo H 250 K \ ¸² ú ½ + É M :
t [ jl _ o \ O . s : r ¸\ " f STM © [ þ t É r Cu(110) ³ ð \ É r cluster[ þ t s + þ A$ í ) a כ ` ¦
Ð . ì ø Í@ / Ð 4.3 eV 4 x Ä ºo _ [ jl H e > : r ¸, 600 K s © \ " f r4 ¤ l r ô Ç . s כ É r 2.1 eV ü < 4.3 eV\ " f RDS ñ o\ @ /ô Ç É r " é ¶ [ þ t s e 6 £ §` ¦ \ V © ½ + É Ã º e .
PACS numbers: 68
Keywords: RDS, Cu(110), F g < Æ& h s ~ ½ Ó$ í , STM
I. " e  ] Ø
s
: rØ æ[ t É r F « Ñì r _ ³ ð > h| 9 1 p x l Õ ü t& h 6 £ x6 x
\ " f ´ ú §s 6 x ÷ & ¦ e l M :ë H \ , s : r Ø æ[ t \ _ ô Ç ³ ð
_ ½ ¨ ¸ x 9 $ í | 9 o\ @ /ô Ç ½ ¨ H ´ ú §s ÷ &# Q M ® o [1]. z ´] j Ð r « Ñ ³ ð É r ¼ # ¨ î t · ú §` ¦ ÷ rë ß m , Ó ü t
| 9
_ : £ ¤$ í s r « Ñï r q õ & ñ \ " f µ 1 ÏÒ q t H s & h _
& h [ þ t` ¦ t ¦ e . ³ ð ï r q ³ ð ì r$ 3 ` ¦ 0 Aô Ç © q
[ þ t É r s : r Ø æ[ t × æ \ 1 l x& h Ü ¼ Ð ¼ # ¨ î ô Ç ³ ð ` ¦ % 3 l 0 AK " f # Q " { 9 y s \ " f s : rØ æ[ t õ " é ¶ & h F C
\ P
É r ³ ð \ e H step s adatom[ þ t \ _ # µ 1 ÏÒ q t
H כ \ @ / # ½ ¨ % i . s Qô Ç © q [ þ t` ¦ 6 £ x6 xô Ç כ [
þ
t s depth profiling [2], ion beam polishing [3], ion beam thin films deposition [4] 1 p x õ ° ú É r z ´+ « >[ þ t s .
þ
j H \ µ 1 ϳ ð ) a é ß & ñ \ @ /ô Ç s : r Ø æ[ t z ´+ « >\ " f s
: r c s : £ ¤& ñ ô Ç { 9 y ` ¦ ° ú ¦ { 9 H â Ä º Å Òl & h Ó
ü
t ½ ¨ ¸\ ¦ + þ A$ í H כ ` ¦ Ð ¦ % i [5]. s Qô Ç ½ ¨
¸[ þ t` ¦ Ðl 0 Aô Ç z ´+ « > É r @ /Â Òì r STM` ¦ 6 x ¦ e .
Õ
ªo ¦ z ´+ « > õ ÐÂ Ò' s : rØ æ[ t Ê ê ³ ð } 9 l \ ¦ ^ ¦ Ã
º e . Õ ª Q z ´r ç ß Ü ¼ Ð ³ ð \ " f { 9 # Q H & ³ © ` ¦
Ð H X < H & h ½ + Ë t · ú § .
∗
E-mail: shkim [email protected]
: r z ´+ « >\ " f H þ j H \ F K5 Å q ³ ð _ ½ ¨\ 6 x ÷ & ¦ e
H RDS(Reflectance Difference Spectroscopy)\ ¦ s 6 x
#
, s : rØ æ[ t` ¦ " f ³ ð \ " f { 9 # Q H & ³ © ` ¦ z ´r ç
ß Ü ¼ Ð S X % i ¦, ³ ð _ } 9 l ü < RDS 4 x Ä ºo [ þ t s
_ ' a > \ @ / # ½ ¨ % i .
II. ÷ m Ç ] M ö
z
´+ « > É r 1 × 10
−10Torr_ l : r / B N` ¦ ° ú H UHV chamber \ " f s À Ò# Q& . Cu(110) r « Ñ H 900 eV Ar
+s
: r_ sputteringõ 650 K\ " f 2ì rç ß _ annealing` ¦ ì ø Í 4
¤ % i Ü ¼ 9, r « Ñ_ L : F M < Êõ ³ ð _ | 9 " f H µ 1 ß ¦ ± ú
Ðî r r] X Á º] (ü < ± ú É r [ jl _ C â ` ¦ ° ú H LEED(low energy electron diffraction) pattern, AES(auger electron spectroscopy) ü < RDS\ ¦ 6 x # S X % i . z ´+ « >\ " f
6 xô Ç RDS spectrometer H Aspnes type` ¦ 6 x % i ¦ [6], chamber \ Â Ò Ã Ì÷ &# Q e # Q in-situ Ð RDS ñ\ ¦ 8 £ ¤
&
ñ % i . RDS ñ H 6 £ § õ ° ú É r d Ü ¼ Ð ³ ð & ³÷ & ¦
∆r
r = 2 r
[1¯10]+ r
[001]r
[1¯10]− r
[001]Cu(110) ³ ð _ F g < Æ& h s ~ ½ Ó$ í ` ¦ 1.5 ∼ 5.5 eV photon
\
-t % ò % i \ " f 8 £ ¤& ñ % i .
-170-
½ ¨ 7 Hë H Cu(110) ³ ð \ Ar
+s : r_ Ø æ[ t ´ òõ – ^ © & ³ 1 p x -171-
Fig. 1. (a) Real part of the RDS spectrum recorded after Ar ion sputtering of the Cu(110) surface for one hour at 350 K and subsequent annealing to the indicated temperatures. (b) Change of the RDS intensity at 2.1eV during annealing. (c) Shift of the RDS peak at 4.3 eV (open squares) during annealing and RDS intensity at 4.43 eV (open circles).
#
Q : r ¸\ " f Cu(110) ³ ð \ @ /ô Ç Ar
+s : r Ø æ[ t õ
annealing z ´+ « >` ¦ RDS ü < VT-STM(Variable Temper- ature Scanning Tunneling Microscopy)` ¦ 6 x # ½ ¨
% i .
III. + s ÇÊ Ý õ m Í º8 ý
Cu(110) ³ ð _ RDS 4 x Ä ºo × æ \ " f 2.1 eV H Cu(110)
³
ð © I [ þ t s _ F g < Æ& h s ÐÂ Ò' µ 1 ÏÒ q tô Ç כ Ü ¼ Ð
·
ú 94 R e ¦ [7] Õ ªo ¦ 4.3 eV H bulk ü < ' aº ) a F g < Æ& h s
~ ½ Ó$ í \ _ ô Ç כ Ü ¼ Ð · ú 94 R e [7]. Fig. 1 É r 350 K
\
" f Cu(110) ³ ð \ 30ì r 1 l xî ß Ã ºf > Ar
+s : r Ø æ [
t( 5 Å q = 1 × 10
13ions/cm
2)` ¦ ô Ç Ê ê, 5 Å q& h Ü ¼ Ð : r ¸
\
¦ ` ¦ 9 " f 8 £ ¤& ñ ô Ç RDS ñ_ os . 350 K\
"
f Ar
+s : r_ Ø æ[ t Ê ê\ , 2.1 eV 4 x Ä ºo _ [ jl ü < 4 x Ä º o
_ 0 Au H ß ¼> % ò ¾ Ó` ¦ ~ Ã Ît · ú § H (Fig. 1a). Õ ª Q 4.3 eV 4 x Ä ºo H ´ ú § É r % ò ¾ Ó` ¦ ~ Ã Î H (Fig. 1a). 7 £ ¤ 4.3 eV 4
x Ä ºo H % \ " f_ RDS ñ H ; ¤ s ´ ú §s o ¦ high energy A á ¤ Ü ¼ Ð 4 x Ä ºo s 1 l xô Ç (Fig. 1c). s r
«
Ñ\ ¦ 800 K Ð annealing` ¦ L : F Mô Ç Cu(110) ³ ð _ Û
¼Ø þ à Ô! 3 ` ¦ r4 ¤ô Ç . Õ ª Q annealing 1 l xî ß \ 2.1 eV, 4.3 eV ü < ° ú s ³ ð _ F g < Æ& h s ~ ½ Ó$ í \ _ # µ 1 ÏÒ q t
H RDS ñ[ þ t É r s : rØ æ[ t õ : r ¸ o\ B Ä º É r â
¾ Ó` ¦ Ð . 2.1 eV 4 x Ä ºo H 300 K and 700 K_ : r ¸
#
3 0 A\ " f & h & h Ü ¼ Ð r4 ¤` ¦ ô Ç (Fig. 1b). Õ ª Q 4.3 eV 4 x Ä ºo H # Q " e > : r ¸(600 K) s © \ " f " é ¶ A \ - t
_ 4 x Ä ºo 0 Au Ð s 1 l xô Ç (Fig. 1c).
Fig. 2. (a) Real part of the RDS signal after sputtering 30 minutes at 45 K and annealing to the indicated tem- peratures. (b) Change of the RDS intensity at 2.13 eV upon annealing. (c) Shift of the RDS minimum intensity at 4.38 eV upon annealing.
Fig. 2 H 45 K \ " f Ar
+Ø æ[ t` ¦ ô Ç Ê ê, 5 Å q& h Ü ¼ Ð 700 K t : r ¸\ ¦ ` ¦ 9 " f 8 £ ¤& ñ ô Ç RDS ñs . 45 K
\
" f s : r Ø æ[ t` ¦ H â Ä º 2.1 eV 4 x Ä ºo H ¢ - a y è F
g(quench) ) a . ì ø Í \ 4.3 eV 4 x Ä ºo H % \ " f_
o H © : r \ " f_ Ar
+Ø æ[ t õ ü < q 5 p w . 5 Å q& h Ü ¼ Ð annealing : r ¸\ ¦ ` ¦ o " f S X ô Ç õ H 2.1 eV 4 x Ä ºo
H 200 K s © \ " f r4 ¤ l r ô Ç (Fig. 2a). ì ø Í \ 4.3 eV 4 x Ä ºo H 200 ∼ 250 K s \ ç ß _ o e
¦, 600 K s © s ÷ &# Q ë ß ¢ - a y r4 ¤ô Ç . 350 K\ " f _ z ´+ « >õ ð ø Ít Ð, s Qô Ç ¿ º 4 x Ä ºo H annealing \
É r â ¾ Ó` ¦ ° ú H כ É r y y _ 4 x Ä ºo _ " é ¶ s B
Fig. 3. (a) STM image recorded after 30minutes sputter-
ing at 45 K. (b, d) STM image recorded after annealing
to 200 K. (c, e) STM images measured after annealing
250 K. The images size of (a), (b) and (c) is 2250 ˚ A ×
2250 ˚ A, while 1000 ˚ A × 1125 ˚ A for (d) and (e). Tunnel-
ing condition : V
t= 1 V and I
t= 1.0 nA.
-172- ô Dz D GÓ ü t o < Æ rt “D hÓ ü t o ”, Volume 48, Number 2, 2004¸ 2 Z 4
Ä
º Ø Ô H כ ` ¦ · ú Ã º e . 2.1 eV peak É r ¯ Y ~ ½ Ó ¾ Ó SBZ(surface brillouin zone) \ > r F H ð ø Í © I \ " f
© I Ð_ F g < Æ& h s \ _ # µ 1 ÏÒ q t H כ s [8]. s 4
x Ä ºo H ³ ð \ > r F H vacancy, step edge[ þ t õ ° ú É r
³
ð _ defect[ þ t \ B Ä º y ¦ · ú 94 R e .
Fig. 3 H 45 K \ " f 30 ì r 1 l xî ß s : rØ æ[ t Ê ê\ 12 K
Ð : r ¸\ ¦ ? / 9" f 8 £ ¤& ñ ô Ç STM © [ þ t s . s : rØ æ[ t Ê ê Cu(110) ³ ð É r B Ä º } 9 # Q4 R e ¦, 40 ˚ A Ð É r is- land[ þ t Ð W = ) e (Fig. 3a). 45 K\ " f H s : rØ æ[ t \ _
# + þ A$ í ) a vacancy adatom[ þ t_ S X í ß > Ã º B Ä º
t Ù ¼ Ð © : r \ " fü < ° ú É r H terrace H % 3 ` ¦ Ã º \ O .
Õ
ª QÙ ¼ Ð s : rØ æ[ t \ _ # µ 1 ÏÒ q t H adatom[ þ t É r Á º
| 9
" f > ( 4 Re H É r island\ ¦ + þ A$ í ô Ç . : r 7 Hë H \
ü < e t · ú §t ë ß , © : r \ " f s : r Ø æ[ tô Ç Ê ê\ 8 £ ¤& ñ ô Ç STM © [ þ t É r step_ density 7 £ x H כ ` ¦ Ð# ï r .
Õ
ª Q ¨ î ç H terrace ß ¼l H ³ ð © I [ þ t` ¦ Ä »t ½ + É ë ß p u
#
y ß ¼> è ß . Õ ª QÙ ¼ Ð © : r \ " f 2.1 eV 4 x Ä º o
_ [ jl y è H step density_ y è\ _ ô Ç כ s ¦, 45 K \ " f_ s : rØ æ[ t É r õ & h Ü ¼ Ð ³ ð © I [ þ t s 8 s ©
> r F t · ú §> ô Ç . õ & h Ü ¼ Ð 2.1 eV\ " f_ RDS
ñ H ¢ - a y quench ) a .
Annealing z ´+ « >` ¦ : x # ³ ð © I \ ¦ è q ë ß p u_
&
ê ø Í terrace\ ¦ ° ú l 0 Aô Ç É r cluster[ þ t_ Ô æ õ H STM Ü ¼ Ð S X ) a . Fig. 3 É r 45 K \ " f Ar
+s : rØ æ[ t Ê
ê 200 K(Fig. 3b, d)ü < 250 K(Fig. 3c, e)\ " f annealing ô
Ç Ê ê\ , S X í ß ` ¦ } ¦ : r ¸\ ¦ 12 K Ð r ? / 9" f 8 £ ¤
&
ñ ô Ç © [ þ t s . cluster[ þ t Ô æ õ ÷ & " f island_ ß ¼l & t
H כ ` ¦ ^ ¦ Ã º e .
2.1 eV ñ_ r4 ¤ É r & ñ S X y 250 K_ : r ¸\ " f r
÷ &% 3 . 250 K\ ¸² ú % i ` ¦ M :, 150 ˚ A & ñ ¸_ ß ¼l \ ¦
° ú
H island[ þ t s + þ A$ í ÷ &l r Ù þ ¡ . s כ É r P. Stoltze et al. [9] \ " f Å Ò# Qt H diffusion parameter ü < ¸ ú ´ ú H .
4.3 eV 4 x Ä ºo H bulk d ½ × ¼_ L @ /g A & h _ H % \ e
H Fermi level E
F ÐÂ Ò' L
u1 Ð_ s ü < ' aº ) a כ s
[7]. Õ ª QÙ ¼ Ð 4.3 eV 4 x Ä ºo H % _ RDS ñ H ³ ð
_ + þ AI (morphology)÷ rë ß s : rØ æ[ t 1 l xî ß \ µ 1 ÏÒ q t H subsurface defect(dislocation, interstitial and Ar
+inclu- sion) \ y . Õ ªo ¦ bulk defect(vacancy cluster)_ annealing : r ¸ H B Ä º Z } . z ´] j Ð 8 £ ¤& ñ ) a 4.3 eV 4 x Ä º
o
_ [ jl r4 ¤ ÷ & H e > : r ¸, 600 K H Cu bulk_ va- cancy clusters \ @ /ô Ç annealing : r ¸ 7 £ ¤, 620 K ü < q 5 p w
[10].
IV. + s Ç Â ] Ø
Cu(110) ³ ð \ Ã ºf > Ar
+s : rØ æ[ t` ¦ # RDS ü
< STM` ¦ s 6 x # ³ ð © I \ ¦ ½ ¨ % i . Ar
+s
: r Ø æ[ t` ¦ " f z ´r ç ß Ü ¼ Ð RDS ñ\ ¦ 8 £ ¤& ñ % i ¦, RDS ñ[ þ t É r ³ ð õ subsurface defect\ y H
כ
õ 2.1 eV 4 x Ä ºo H ³ ð _ defect\ y ¦, 4.3 eV 4
x Ä ºo _ ñ H subsurface defects \ y H כ ` ¦ S X
% i .
Y c
p w à U Ø ô
[1] M. V. Ramana Murty, Surf. Sci. 500, 523 (2002);
T. M. Mayer, E. Chason and A. J. Howard, J. Appl.
Phys. 76, 1633 (1994).
[2] A. Zalar, B. Pracek, P. Panjan, Surf. Interface Anal.
30, 247 (2000).
[3] X. W. Zhou, H. N. G. Wadley, Surf. Sci. 487, 159 (2001).
[4] M. Wissing, M. Holzwarth, D.S. Simeonova- Snowdon, K. J. Snowdon, Rev. Sci. Instr. 67, 4314 (1996).
[5] S. Rusponi, G. Costantini, C. Boragno and U. Val- busa, Phys. Rev. Lett. 81, 2735 (1998).
[6] D. E. Aspnes, J. P. Harbison, A. A. Studna and L.
T. Florez, J. Vac. Sci. Technol. A6, 1327 (1988).
[7] L. D. Sun, M. Hohage, P. Zeppenfeld, R.E. Balderas- Navarro and K. Hingerl, Surf. Sci. 527, L184 (2003).
[8] K. Stahrenberg, Th. Herrmann, N. Esser and W.
Richter, Phys. Rev. B61, 3043 (2000).
[9] P. Stoltze, J. Phys. Condens. Matter. 6, 9496 (1994).
[10] M.W. Thompson, Defects and Radiation Damage in
Metals (Cambridge University Press, London, 1969),
p. 322.
½ ¨ 7 Hë H Cu(110) ³ ð \ Ar
+s : r_ Ø æ[ t ´ òõ – ^ © & ³ 1 p x -173-
Effect of Ar + Ion Bombardment on the Morphology of Cu(110)
S. H. Kim
∗and C.-Y. Park
Department of Physics, SungKyunKwan University, Suwon 440-746
L. D. Sun
Department of Physics, Linz University, Austria, A-4040 (Received 30 December 2003)
Ar
+ion bombardment and annealing of the Cu(110) surface have been studied by using reflectance difference spectroscopy (RDS) and scanning tunneling microscopy (STM). Ion bombardment of the Cu(110) sample at 350 K and 45 K totally destroys extended terraces and leaves behind a rough surface covered with small clusters. The RDS signal at 2.1 eV is completely quenched whereas the position of the 4.38-eV peak shifts to higher energy upon sputtering. This shift can be related to the density of the vacancies in the subsurface region. The RDS signal at 2.1 eV shows no change until the annealing temperature reaches 250 K. At this temperature, the STM images reveal the formation of small terraces on the Cu(110) surface. In contrast, the recovery of the 4.3-eV peak exhibits a threshold temperature as high as 600 K. This evidence suggests that two different mechanisms are responsible for the variations of the RDS signals at 2.1 eV and 4.3 eV, respectively.
PACS numbers: 68
Keywords: RDS, Cu(110), Optical anisotropy, STM
∗
