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ÂÉì»µ½ V1|xWxO2 ÅCZxÌæÜÅ W6{ uFig. 1

Schematic phase diagram of V1|xWxO2/TiO2(001) thin­lm
and schematic gures of crystal structures. Large (small)
spheres indicate V (O) ions. Dotted lines represent octahedraof oxygen ions. Blue thick lines indicate V dimers.

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Fig. 2 Temperature dependence of (a) resistivity, and (b) c­lattice
constant of the sample with x0.065, 0.09, and 0.11.

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ÅÍCÀÛÉ X üUN]ÚªÏª³ê½ V1|xWxO2 @ÅdCïR¦ðªè·é½ßCNCIX^bgÌdÉÌ x0.065ðSÆµÄCsÁ½À±yÑ»êçÌð|[gÉzüðÊµ½B
Oqµ½ððgÁÄì»³ê½Íú³80 nm ÅCÍÉÂ¢ÄÌà¾ðs¤B

tHg\OtB[ZpÅfoCXÌp^[jOðs¢C³çÉ Au/Al ÌÏw^dÉª^óöi±IÈ X üUN]ÚÉ¨¯édC`±xÆ»\¢ÌÏ»³êÄ¢éBÚ×ÈÌì»û@ÉÖµÄÍCaJçÌ_¶ 9, 15ÉÚµ¢ÌÅC»¿çðQÆ¢½¾«½¢B

X üÆËºÅÌdCïR¦yÑ X üñÜÌ¯ªè
X üÆËºÅÌ¿ÌdC`±xÆ»\¢ÌÏ»ð¯ªè·éÉÍCFig. 3(a)Ìæ¤ÈfoCXÁH³ê½

V1|x Wx O2 É¨¯éâÌà®]ÚðºÁ½ X üUN\¢]Ú

ðp¢CüË X üªð®µ½óÔÉ·éKvx0.065Ì V1|xWxO2 ÉÎµÄdCïR¦Æ c ²·

éBäXªgpµ½9.8 keV Ì X üÉ¨¯éÎÛ¨¿Ì¯ªèðsÁ½BAu\[o[ÅüË X üÌ­xðª

VO2 ÖÌNü·Í30 mm öxÅ

é½ßCÊíÌoN

¿ÅÍ¿SÌÌêlÈÏ»ðÏª·é±ÆªÅ«È²®µCX üUN]ÚªN±çÈ¢æ¤ÉlÅéÔÏZlÅ1014 photon/cm2 É½È¢tHgtb¢BäXÌO[vÅÍCX üÌNü·æèà¢ú³

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80 nm öxÌ VO2 ¿ðúËõÌr[TCYæè

t@CyÑ»±©çß½ c ²·ÍCFig. 4 ÌüÅ¬³¢200 mm~100 mm öxÉfoCXÁHµCFig. 3(b)¦³êÄ¢éB\ªá·Ì 9 K É¨¢ÄÔÏZlÅ1014Ìæ¤ÈZbeBOÅ X üÆËºÉ¨¯édCïR¦photon/cm2 ÈãÌtHgtbNX§xÌ X üðÆËµ½CFig. 4(c)ÌÂüÅ¦³êéæ¤È(0 0 2)½ËÌv

yÑ X üñÜÀ±Ì¯ªèðsÁ½B
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ÚãÌ c ²·ÍC~·Éæé\¢]ÚªN«éOÌ140

é9.8 keVK ÌlÜÅ¸­µÄ¢½BÜ½C¯ÉÏªµ½dCï[µ½BñÜ X üyÑdCïR¦ÌªèÍCåR¦àCâÌÖÌ]ÚªN±éOÌà®ÌlÆ¯¶

É(0 0 2)î{½ËßTÅs¢CüË X üÌr[TCY®ç¢ÜÅÉ¸­µÄ¢½BÈãÌæ¤ÉCV1|xWxO2 

Á½BüË X üÍtHg_CI[ÅÍCá·Å­¢ X üðÆËµ½±ÆÉæèâÌ©

ÂÌî{½ËÆ´iq½ËªÏªÂ\ÅÉ`Íñ500~600 mm2 Å

12 photon/cm2 sec ÌtHgtçà®IÈdCïR¦ÌÏ»ðº¤\¢]ÚªÏª³ê

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hðp¢ÄªèµCñ10@ðp¢Ä¿Ì·xð§äµCÜ½C4 [qyÑ 2 [qÊuÌÏ»Í50 K tßÜÅ¸··éÆÁ¸µ½B50 K ÈãÉ¸·µCÄxá·Éº°Ä­¢ X üðÆË·éÆÄÑ X üUN]ÚÍÏª³êéBÏª³ê½ X üUNÌâÌà®/\¢]ÚÍC¼Ì¨¿ÅÏª³êÄ¢é XüUN]ÚÆ¯lÉCFig. 5 Å¦³êÄ¢éæ¤ÉPÊÔ

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äáµÄN±ÁÄ¢é±Æª»¾µ½B±±ÅÍá·Ì 9
K É¨¢ÄCFig. 4(c)ÌüÌ(0 0 2)½ËÌs[NgbvÊuÉfBeN^[ð\¦Cs[Ngbv­xÆdCïR
¦Ì X üÆËÔÌË¶«ð¯ÉªèµÄ¢éBFig. 5ÌFªÅ 1~1012 photon/cm2 sec öxÌ­¢ X üðÆËµÄ¨èC»ÌÔÑÌÝÅñÜ X üÌ­xÆdCïR¦Ì¸­ª©çêéBX üÌÆËðâ~µ½ÌdCïR¦Íá±ã¸XüÉ

éª®SÈâÌóÔÉÜÅ

Íñ¹¸Cà®óÔÜÅ]Úªis·éÆi±IÉ
Fig. 3(Color online) (a) A top­view photograph of the patterned
V1|xWxO2 lm attached with Au/Al electrodes. The graysquare indicates the area of x­ray irradiated region (`500~
600 mm2). (b) Schematic view of the conguration of thesimultaneous measurements of resistivity and x­ray dirac­tion.

iªèµ½ÀèÔÈãÍj»ÌóÔª±¢½B
X üUNÌà®ÖÌÏ»ÌÚ×ÈJjYðð¾·é½ßC»ÌßnIÈóÔðÚ×É²×½BFig. 6 ÍC
X üUN\¢]ÚÌßnóÔÉ¨¯éñÜvt@Cð¦µÄ¢éB»ê¼êÌf[^Í¶÷É¦³ê½ÔúËõ Nov. 2013 Vol.26 No.6  311

Fig. 4Temperature dependence of (a) resistivity, (b) c­lattice con­stant, and (c) diraction peak prole of (0 0 2) reection ofx0.065. In all panels, black curves and dots show the datain heating runs without irradiation of strong x­ray. Blue
curves and dots indicate the data in heating runs after irradi­
ation of strong x­ray at 9 K.

Fig. 5

X­ray exposure­time dependence of the resistivity and the in­tensity of (002) diraction peak in the insulating phase. The
photon ux density was `1~1012 photon/cm2 sec. The x­
ray was intermittently irradiated during the periods ascolored with light blue. The reduction of the insulating phaseoccurs only under the x­ray irradiation but with negligible
relaxation during the x­ray turno period.

Fig. 6

X­ray exposure­time dependence of the peak prole of (0 02) reections of x0.065. The exposure­time of strong inci­
dent x­ray is indicated for each data. The observed dirac­tion patterns with multi­Gaussian tting as composed of in­sulating (light blue), phase separated (dotted gray), andmetallic (dark blue) components.

¾¯ 1~1012 photon/cm2 sec ÈºÌ X üðÆËµC»ÌãAu\[o[Å\ªÉ¸³¹½üË X üðgÁÄñ
Üvt@CðªèµÄ¢éB¾çê½ßnóÔÌñÜ
vt@CÍCuªð\æèàªL¢ 3 ÂÌKEVAÖÅtBbeBOÂ\ÅÁ½B3 ÂÌ¬ªÍs[NÌ qÞÊuæèâÌóÔiW¢FüjCà®óÔiZ¢ÂFüjCÔóÔiDFÌ_üjÅ

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ÈãÌ¼èðîÉµÄCßnóÔÉ¨¯é X üUNà®yÑâÌÌ(0 0 2)½ËÌs[Ngbv­x©çX üÌ±ÂÂ\È£æè·¢}CN[gXP[ÌÏª¦ðvZµ½Ìª Fig. 7 ÅÅª£µÄ¢é±Æªl¦çêéBÜ½CÔóÔÌÌÏª¦ÌÝ\¦jBFig. 7 ÌÛÍCFig. 6 Å¦³ê½ 3

éiX üUNà®Ìs[NÊuÍ X üÌÆËÔÉ¶ÄÏ®·é±ÆªÏ

ÂÌ¬ªÌ­xäÆs[NÊu©çvt@CÌdSÊª³ ê ½B â Ì  Æà ®  Ì 2  f Ì ¼ è ÌºuðßC¾çê½dSÊuÆ X üUNà®yÑâÅC»êçª X üÌ±ÂÂ\È£æèZ¢im[gÌÌÌÏª¦ª¼üIÉµÄ¢éÆl¦ÄðÍ³êXP[Åª£µÄ¢éêÍCeÌ»\¢ð½½f[^ÅéBX üÆËÌ X üUNà®ÌÌÏªÏ»µ½ñÜvt@CªÏª³êé14) B»Ì½ßC

¦ÌÆËtHgtbNX§xÉæéÏ»ðc_·é½ÔóÔÅÍâÌÆà®ÌÌÏäÉäáµÄs[NßC312  úËõ Nov. 2013 Vol.26 No.6

F ü Å¦ ³ êé 4 Ö  Åt B be B  Oð sðà ¡ W h[v VO2 É¨¯éâÌ©çà®ÖÌÏ»ðº¤ X üUN\¢]Ú

Fig. 7

Fig. 9The conductivity and the metal volume fraction are plotted
as a function of the total x­ray dose.

Fig. 10

The relation between the conductivity and the metal volume
fraction. The black line indicates a tting result with a rela­tion that ss0~(V_VC)S. The critical percolation volume(VC) is around 5÷ and the exponent S1.5.

Metal volume fraction vs peak­top­intensity of (0 0 2)
diraction for the insulating phase. The light­blue line shows
the result of tting with an arbitrary function for the data
mining procedure to deduce the metallic volume fraction
from the diraction intensity.

Ì(0 0 2)½ËÌ­x©çCFig. 6 Æ 7 ÌðÍÊæè¾ç
ê½·Z®ðg¤ÆC»ê¼êÌÌÌÏª¦ÌÆËÔË¶«Í Fig. 8(b)Ìæ¤Éßé±ÆªÅ«½B
Fig. 8Time dependence of (a) the peak­top intensity of (0 0 2)
diraction and (b) volume fraction. The light blue and black
curves are measured at the peak­top­position of (0 0 2)
diraction in the metal and insulator phases, respectively.

Fig. 9 Í¯ªèÀ±æèß½dC`±xÆ X üUNà®ÌÌÏª¦ÌÆËtHgtbNX§xË¶«ð¦µÄ¢éBFÅ¦³êédC`±xÍCÔÏZlÅ
2~1014 photon/cm2 öxÌ X üªÆË³êéÆåµnßC1016 photon/cm2 Ì X üÌÆËãÉÍOaµÄ¢éBêûCFüÅ¦³êé X üUNà®ÌÌÏª¦Í 3¢Ci0 0 2)½ËÌs[Ngbv­x©ç¼Ú X üUNà~1013 photon/cm2 öxÅåªÏª³êÄ¨èCX üU®yÑâÌÌÌÏª¦ð·ZÅ«éÖðèµ½B

Nà®ÌÌÏª¦ÆdC`±xÌÉÍ¾ç©È·ªâÌÆ X üUNà®ÅÏª³êé(0 0 2)ñÜ­¶¶Ä¢½BxæèC»êçÌÌÏª¦ðvZµC»ê¼êÌ X üÆ±Ì X üUNà®ÌÌÏª¦ÆdC`±xÌÖWËÔÌË¶«ðèµ½BFig. 8(a)ÍCâÌÆ X ü

ððÍ·é½ßÉCFig. 10 É¦·æ¤ÉÆËtHgt

UNà®É¨¯é(0 0 2)½ËÌs[Ngbv­xÌ X

bNX§xð}îÏÆ·é¼ÒÌÖð²×½Bp[RüÆËÔË¶«ÅéBX üÆËÔÌoßÆÆàÉ

[V_ÉîÃ­dC`±xÍCdC`±x sCWâÌÌ(0 0 2)½ËÊuÌ­xÍ¸µCX üUNà s0 CX üUNà®ÌÌÏª¦ VCp[R[V®Ì­xÍåµÄ¢éBâÌÆ X üUNà®l VCCp[R[Vw S ðp¢ÄCss0~(V_úËõ Nov. 2013 Vol.26 No.6  313

Fig. 12Fig. 11

Schematic illustration of percolation behavior associatedwith x­ray induced insulator­metal transition in W­doped
VO2 thin­lm. Light blue spheres indicate x­ray induced
metal regions in the sample.

Temperature dependence of c­lattice constant of x0.11
sample before/after irradiation of strong x­ray.

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bÆËµ½Ì(0 0 2)ñÜüÌvt@CÌÏ»ð¦314  úËõ Nov. 2013 Vol.26 No.6

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Fig. 13

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where x­ray induced metallic phase is observed.

Fig. 15

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1)

M. Nakano, K. Shibuya, D. Okuyama, T. Hatano, S. Ono, M.
Kawasaki, Y. Iwasa and Y. Tokura: Nature 487, 459 (2012).
2) Y. Tokura: Rep. Prog. Phys. 69, 797 (2006).

úËõ Nov. 2013 Vol.26 No.6  315

3)
4)
5)
6)
7)

8)
9)

10)

11)

12)
13)
14)

V. Kiryukhin, D. Casa, J. P. Hill, B. Keimer, A. Vigliante, Y.
Tomioka and Y. Tokura: Nature 386, 813 (1997).
D. E. Cox, P. G. Radaelli, M. Marezio and S­W. Cheong:Phys. Rev. B 57, 3305 (1998).
V. Kiryukhin, Y. J. Wang, F. C. Chou, M. A. Kastner and R.
J. Birgeneau: Phys. Rev. B 59, R6581 (1999).
Y. Yamaki, Y. Yamasaki, H. Nakao, Y. Murakami, Y.
Kaneko and Y. Tokura: Phys. Rev. B 87, 081107(R) (2013).
H. Ishibashi, T. Y. Koo, Y. S. Hor, A. Borissov, P. G.
Radaelli, Y. Horibe, S­W. Cheong and V. Kiryukhin: Phys
Rev B 66, 144424 (2002).
T. Furubayashia,, H. Suzukia, T. Matsumotoa and S. Naga­
ta: Solid State Commun. 126, 617 (2003).
K. Shibuya, D. Okuyama, R. Kumai, Y. Yamasaki, H.
Nakao, Y. Murakami, Y. Taguchi, T. Arima, M. Kawasaki
and Y. Tokura: Phys. Rev. B 84, 165108 (2011).
D. Okuyama, K. Shibuya, R. Kumai, Y. Kitagawa, T.
Suzuki, Y. Yamasaki, H. Nakao, Y. Murakami, M.
Kawasaki, Y. Taguchi, T. Arima and Y. Tokura: to be sub­mitted.
G. Villeneuve, A. Bordet, A. Casalo, J. P. Pouget, H.
Launois and P. Lederer: J. Phys. Chem. Solids 33, 1953
(1972).
T. Horlin, T. Niklewski and M. Nygren: Mater. Res. Bull. 7,1515 (1972).
T. Horlin, T. Niklewski and M. Nygren: Mater. Res. Bull. 8,179 (1973).
K. L. Holman, T. M. McQueen, A. J. Williams, T. Klim­
czuk, P. W. Stephens, H. W. Zandbergen, Q. Xu, F. Ronning

15)
16)
17)

18)

19)
20)
21)

and R. J. Cava: Phys. Rev. B 79, 245114 (2009).
K. Shibuya, M. Kawasaki and Y. Tokura: Appl. Phys. Lett.
96, 022102 (2010).
Y. Muraoka and Z. Hiroi: Appl. Phys. Lett. 80, 583 (2002).
A. Cavalleri, Cs. T áoth, C. W. Siders, J. A. Squier, F. R áaksi,
P. Forget and J. C. Kieer: Phys. Rev. Lett. 87, 237401(2001).
A. Cavalleri,, M. Rini, H. H. W. Chong, S. Fourmaux, T. E.
Glover, P. A. Heimann, J. C. Kieer and R. W. Schoenlein:
Phys. Rev. Lett. 95, 067405 (2005).
S. Kirkpatrick: Rev. Mod. Phys. 45, 574 (1973).
S. Mascarenhas, D. A. Wiegand and R. Smoluchowski:
Phys. Rev. 134, A481 (1964).
H. N. Hersh: Phys. Rev. 148, 928 (1966).

ÒÐî
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Æ§s­@l»w¤n­¨«Èw¤Z^[ ¤õE­mail: okuyamariken.jpêåF\¢¨«CÅÌ¨
mªðn
2007Nkåwåw@w¤È¨w
êUC¹CmiwjBÈwZpU»@\ ERATO ¤õC»w¤î²¤¤õðoÄC2013N 4 æè»EB

X­ray induced structural phase transition
accompanying insulator­metal transition inW­doped VO2 thin­lm
Daisuke OKUYAMA1, Keisuke SHIBUYA2, Reiji KUMAI3, Yuichi YAMASAKI3,
Hironori NAKAO3, Youichi MURAKAMI3, Yasujiro TAGUCHI1, Takahisa ARIMA1,4,
Masashi KAWASAKI1,5 and Yoshinori TOKURA1,5
1RIKEN Center for Emergent Matter Science (CEMS), Wako 351_
0198, Japan

2National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305_
8562, Japan

3Condensed Matter Research Center and Photon Factory, Institute of Materials Structure Science, KEK,

Tsukuba, 305_0801, Japan

4Department of Advanced Materials Science, University of Tokyo, Kashiwa 277_
8561, Japan
5Department of Applied Physics, University of Tokyo, Tokyo 113_
8656, Japan

Abstract

Materials with external­eld­induced­phase­transition have been extensively studied because of ainterest of the driving mechanism of its phase transition and a potential for a device application.
From our recent research, it is claried that the persistent x­ray induced phase transition takes
place at low temperature in the two insulator phases on electron doped VO2 thin­lm. In this rev­iew, we will report that how the bulk resistivity is aected by the local structural phase transition
induced by the x­ray irradiation with the explanation of the simultaneous measurement of resistivi­
ty and x­ray diraction under the x_ray irradiation and the analysis method of obtained data.

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