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Development of a crack gauge by using ion beam mixing
Nuclea! Instruments and Methods in Physics Research 980/81 (1993) 1308-1312 North-Holland
Ui~ LKul,- B
Beam Interaoti nna with Mate, ials S,Atoms
Development of a crack gauge by using ion beam mixing S. Ohno, N. Shigenaka, ivi . Ftise and H. I[)c Energy Research Lahowiory, Hitachi Lid.,
1168 Hitachi. 16awki, Japan
The in . beam T:~ci .^.g ~eCh^'rise ha " `ten applied to develop a crack ;;auge. This gauge con-ls of an array of insulator/conductor bands on an insulating substrate which 's attccheu to the test p~erx . The principle of a gauge is based on the measurement of resistance change brought by cutting of , nduOive bands due to crack growth in the test piece . An array of insulator/conductor sets was formed by ion bombardment on a chin conductor layer which had been evaporated onto the insulator substrate . I,or the insulator substrate, SiO, was used, and Ru was the conductor . An array patter; was produced with a mask by separating the ion beam . To confirm our idea, a crack gauge of 8 v 8 mm was fabricated on a compact tension test piece of stainless steel . The spacing of the conductive bands of 0 .1 mm width was 0.1 rrrcn . To measure the resistivity, thin multdayers of Si(5 nm)/Ru(S(1 ttm)/Si(30 nin)/SiO,(300 nm) films were mixed by 300 keV Xv' ions The resistivity of the mixing region was I )and to change drastically at the dose of 7xI0r° Xe'/cm`. When the test pie cracked under tension, the gauge measured the crack length with good accuracy. 1. Introduction Ion heart . mixing, which utilizes the kinetic energy of ions to mix predeposited surface layers with substrate matzrials, ha:" greatly expanded the potential uses of ion beams to modify materi;Is properties [1,2]. Recently, this technique has been applied to metal-insula'or systems where interest has focused on the finding that ion bombardment often increases the adhesion of the film to the substrate and the resistivity at the ion mixed region [3-5]. It is also possible to create lecar ized mixing products by ion bombardment with a micro-ion beam or an ion beam through a mask [6]. 'Me have undertaken the present investigation tct verify that an insulator/ conductor array can be formed in a metal- insulator system by bombarding with ion beams through the mask The technique was applied to construct a crack gauge which was attached to a compact tension (CT) test piece . An ordinary crack gauge with metal-insulator array formed on insulator substrate is attached to a test piece by an adhesion method. The crack length can be measured with the use of the resistance change caused by cutting of an array . However, the adhesion of the gauge under high-temperature (above 200°C) or wet conditions is apt tc be destioyed. and the reliabi!ity of the gauge being used tinder !hcsc conditions is low. The present m ".thod provides us a means of constructing a crack gauge . 2. Construction of the gauge The principle c( the crack gauge is based on the change of composite resistance of conductor/ insulator
hands induced by cutting of the bands by crack growth . Resistance increases stepwise only when _,onductor bands arc cut. The crack length can be derived from the number of steps caused in the gauge . The concentration of the crack gauge developed by the ton beam mixing technique is illustrated in fig . l . i n order to fabricate the crack gauge, at first, an insulator film was deposited by electr^n-!-2am evaporation on the CT test piece. Subsequently, a conductor film was deposited onto the insulator 1 11 im . : h,afiy, the spe,imens thus formed were irradiated through the mask with a .:et of aligned slits to form an array of insulator,/ conductor bands on th^ test piece . The bornbar6cd region was ion-mixed at,d this resulted in a rcsistl"ity increase. For insulator film SiO, was used, and Ru was the conductor film because their mixed products were expected to be a good insulator. Prior to forming the insulator/ conductor array, irradiation conditions such as ion dose to alter the mixed region into insulator were determined by measuring the resistivity of the mi. - pd r gion . A thin multilayered sample was used for this i,zr,lsuremcnt . It had 5 nm Si, 50 nm Ru and 30 nm Si layers deposited on a single crystal of Si on which the surface had been oxidized. The ovide laver was Ski, with a thickness of 300 nm. A Si layer was kept between SiO, and Ru layers in order to avoid their mixing by th^, rmal diffusion (see fig . 2) . This sample is called the Si/Ru/Si/SiO, sample in the following . Ion-beam-induced mixing was carried out by irradiation of 300 keV Xe' ions at 300 K vvith doses ranging from 0 to f; x 10" Xe'/cm` .'Thc Xc' current density was 2.2x lO t ' Xe'/cm = s in all cases . The in-sits observation of resistivity under irradiation was per-
0168-583X/93/$06 .00 C 1993 - Elsevier Science Publishers B .V. All rights reserved
S Ohno et ai. ! Dt Llptnew osa crackgauge by using ion beam tnixmg
Fi1;. 1 . Ct-,t - action
1309
precedure of the crack gauge attached to the C- 1' test piece by using 4,1 ion beam mixing technique .
formed by using a conventionally aligned four-point probe method . Synchronously with the resistivity measurement, RBS analysis of the Si/Ru/Si /Si02 sample was performed at cacti dose to determine the depth profile . To verify the formation of the insulator/ conductor array, the Si/Ru/Si/SiO, was irradi.rtcd through a mask with a set of slits of 0 .1 mm width . ï'he separation among the slits was 0.1 mm, as shown in 1. 3. Results and discussion
Si/Ray/Si sample increased with dose until 5 x lo t s Xe + /cm 2 , and saturated at a value of 6 .5 x 10 -4 S1 CM . RBS analysis was done for th,- Sa/Ru/Si sample irradiated with doses of 0, 1 X 10 15 and 1 .2 X 10 16 Xe }/cm= . These results are shown in fig. 5 . Above 5 X 10 15 X, `/cm 2, the composition of the mixed layer was approximatoly found to be Ru 2 Si 3. Ru-silicide (Ru 2 Si ;) ;vas produced by mixing of Si and Ru. Its resistivity was a f;vr time " la-ger than that of Ru, and the resistivity did got increase significantly if no oxygen was present in the mixed region .
3.1 . Resistivity change Resistivity data as a function of dose arc plotted it fig. 2 . The resistivity slowly increased with dose up to 7 X 10 1" Xc + /cn12 . Above this valu,-, the resistivity incrcase .i drastically to 0 .05 11 cm, and then tended 1o bt saturated . Results of RBS analysis of irradiated Si/Ru/Si/SiO, samples are shown in fig. 3 . The doses of two analyzedpoints ((1) and (2) in fig. 3) correspond to 2 X 10 1" and 7 X 10 1 ° Xe + /cm 2 , respectively . The mixed region appeared it , both cases and mixing progressed with increasing dose. Above 7 X 1016 Xc + /cm2 , the mixed region had an approximate composition of RuSi0- It is significant that the amount of oxygen diffusing towards the surfat,, increased with done . To investigate the reason why the resistivity of the mudd rt" vion increased in the case of the Si/Ru/St/SiO, sample, the resistivity change by ionbombartlment was measured with a reference sample, which is called the Si/Ru/Si sample in the following and consisted of 5 nm Si, end 50 not Ru layers on a Si wafer substrate . This rest,it is plotted in fig . 4. Irradiation conditions were the ,?me as those for the Si/Ru/Si/SiO, sample . T:te resistivity of the
(X10-2 ) 7
I-
EU C
i 5~ 4
r
3uoäcv xc Sv 5nm Ru 50cm _
Si :80nm
_, ~ 3Ô0 nm semplc Si/Ru/ .i/Si02 .
0
L
0
j - -7=__' __ _L _
3
Dise
4
5
6 (Xe+/cm 2)
7
8
1
9 (X1016 )
Fig. 2. Resistivity change of the Si/Ru/S'/S'()2 sample during irradiation with 300 keV Xe + ions at a current density of 2.2X 10 13 Xe + /cm 2 s. (1) and (2) show RBS-analyzed points ccrre~ponding to 2X 10 16 and 7.2X 1111^ Xz'/cm2 , respectively . Va . NOVEL TECHNIQUES (a)
1310
S. Oh- er ct / ()-rlnnmem ,,f a rraek Dose :
2.OX10' b
(Xe+ /cm Z )
garrge by a fing iori bemn rnWng
(1) Dose -~ 100
:
0
(Xe'/cm')
t
50
_v
U
Bv
0L
0
~i 20
11 40
60
80
100
12U
~2) Dose - 1 .0X10' 5 ();e~/(:m Z) 100--- ~-_ -
0
20
40
60
20
100
ï20
100
120
D,se
100-
C O '7t)
73
C
d U C O
U
U 0i
~_ .
J
50
----_--------i
20
-i0
60
80
Depth (nm) Fig . 3. RBS analysis of Si/Ru/Si/ SiOO Z sample with doses of 2x 1016 (1) and 7.2 x 10 16 Xe'/cmZ (2).
Depth (nn-.) Fig . i . RBS analysis of Si/Ru/Si san!ple with doses of 0 (1), I x 10 'S (2) and 1 .2x 10 16 (3) Xe`/cm' . The pieseure in the target chamber during irradiation was 7.2X 10 " Tui r . Os;gen could not be detected by RBS analysis.
From these re-~:ts, the large increase of resis?^ ,tt:,, in the case of the Si/RU/Si/S'02 sample was expected to be caused by production and thickening of
an insulating layer (SiRx'OZ ) by ditfusion of oxygen from die S'OZ layer into the Ru layer caused by ion mimag . Consùquently, liw cGndductuf layer became
0
40
80
120
160
200
240
280
(X10 -4 ', 9 r-
Fig. 4. Resistivity change of Si/Ru/Si sample during irradia tion with 300 keV Xe' ions at .a current density of 2 .2x 10" Xe'/cm Z s . (1), (21 and (3) show RBS-analyzed points corresponding to 0, 1 Y 10' s and 1 .2x 10 16 Xe `/cmZ, respectively.
Fig, 6 . Result of EPMA analysis for Si/Ru/Si/S'O Z sample irradiated with 300 keV Xe' through a metallic mask with a set of slits of 0.1 mm width after the Ru layer was removed by polishing . The achieved dose was 7 .OX 10 16 Xe'/cmZ . The signal of Ru was detected only in the mixed region .
S Orno er vl. / Develop-
1- .6
m
s
Cracklent t `i 0.1 Iw0.3 0.5
cf a c, ark gauge by using tonlearn mixing
(mm)
0.7
Crack ler_ ch 0.3 0.5 0.20 0'1
am
19.4
F-
Û
Û N ô d
V
mc
É
.f
V d N C N N
.N tr
0
50
1311
100
E.
F
0 .0~
(mm)
0.7 (b,
I
1
0
100
50
Cu-um time (see)
150
150
Cutting time (sec) Fig. 7. (a) The observed resis ante change of a crack gauge (eompostd resistance of all insulator/conductor band.) with crack growth. The resistance wa , measured with a constant current of 0.1 A . (b) The differential of the resistance change of (a) . thinner with increasing dose. It was deauced that the resistivity ~apid :y increased, because the resistivity is inversely proportional to the conductor layer thickness. This is still being investigated in more detail .
n w, t . was obtained front the number of bands. From th Esc results, it was concluded that bands were cut in acc,irdance with the crack growth.
3.2. Test pe "forrnance
4. Conci .lsiop
The Si/Ru/Si/Si0 2 sample was irradiated with 300 kcV Xe + through a metallic mask . The achieved dose was 7 x 10 1" Ae + /cm 2 . Fig . 6 shows the results of EPMA analysis for the irradiated sample after the Ru layer was removed by polishing . The signal of Ru was detected only in the mixed region . From this, it was confirmed that spreading of a narrow mixed layer outside the irradiated area did not c.;-ir . The width of the band was 0 .1 mm. The sample with a conductor/ insulator pattern .v w, cut in the direction perpendicularly to the band . The observed resistance change with progressing array cutting is shown to fig . 7a. Resistance was measured with a constant cur "eut of 0.1 A. The differential of the curve is depicted in fig. 7b. The e ;tcep peaks in fig. 7b correspond to the full cutting of one conductive band, From these results, it was thought to be possible to measure t6, crack length with an accuracy of 0 .2 mm (the sum of an insula,or and conductor band width) by using the insulator/ conductor pattern formed by ion beam mixing. Fig. 8 is a SEM observation of the crack gauge, which was formed by using ion beam mixing, and attached to the CT test piece, which was cracked under tension . The crack length was derived from the number of bands that were cut . After that, thin films consisting of Si/Ru/Si/Si02 layers were removed by polishing . The length in the test piece was measured by SEM observation. This value coincided with the crack length
A crack gauge was produced by using an ion beam mixing technique . The gauge consists of insulator/ conductor bands in an array on an insulator film attached to a CT test piece . The following results were obtained; 1) At a dose of 7 x 10 16 Xe `/cm 2, the resistivity of the mul,ilayered sample with Si/Ru/Si/Si02 layers increased rapidly. The resistivity increase resulted in
mixed region non-irradiatied region
100Nm
Fig. 8 . SEM observation of insulator/comiuctoi bands of the crack. gauge on the CT test piece aft^r introduction of a fatigue crack. Va. NOVEL TECHNIQUES (a)
1312
S Ohno er al. / D-. r,pmen , of a crackgauge
thickening of the insulator layer with increasing dose . This insulator layer was produced by diffusion of oxygen into the conductor layer. The rapid increase of resistivity was due to the fact that the rcsi " +ivity is ... __ .heck inversely .~ ~, proportional . ' ... . . ... ..,.. to tire Cî~ïejia .tvï lay .m ua.nlïSS .
2) An insulator/conductor array with spacing of 0.1 mm was form,,..d by using the ion beam nixing technique. 3) It was verified that the crack length was treasured by the gauge attached to the CT te"t piece with good accuracy .
by using ion
beam , ruing
References [Il F.W. S" aris, C .J. Mcliargue, R. K, .,sowsky and W.O. Hofer, .',,,pl . Sei . 1T, (1989) 103. [2] R.P. De Avillez, LA. Clevenger and C.V . 'rompsort, J. Mater . Re~. 5 (1990) 593. [31 X.X. Xl, Nucl. Instr. a^d Meth. B30 (1988) i6 . [41 A Perez, E. Ah-neau, G t uchs and M. Treilleux, Nucl Instr . and Meth . BCî (1-192) 129. [5l J.E.E. Baglin, Nuci. lnçtr . anu Meth . B65 (199D 119, [61 R.E . Beneson and P. Berning ';ilcl . Inst -. and Meth. B45 (19911) 519.
Ui~ LKul,- B
Beam Interaoti nna with Mate, ials S,Atoms
Development of a crack gauge by using ion beam mixing S. Ohno, N. Shigenaka, ivi . Ftise and H. I[)c Energy Research Lahowiory, Hitachi Lid.,
1168 Hitachi. 16awki, Japan
The in . beam T:~ci .^.g ~eCh^'rise ha " `ten applied to develop a crack ;;auge. This gauge con-ls of an array of insulator/conductor bands on an insulating substrate which 's attccheu to the test p~erx . The principle of a gauge is based on the measurement of resistance change brought by cutting of , nduOive bands due to crack growth in the test piece . An array of insulator/conductor sets was formed by ion bombardment on a chin conductor layer which had been evaporated onto the insulator substrate . I,or the insulator substrate, SiO, was used, and Ru was the conductor . An array patter; was produced with a mask by separating the ion beam . To confirm our idea, a crack gauge of 8 v 8 mm was fabricated on a compact tension test piece of stainless steel . The spacing of the conductive bands of 0 .1 mm width was 0.1 rrrcn . To measure the resistivity, thin multdayers of Si(5 nm)/Ru(S(1 ttm)/Si(30 nin)/SiO,(300 nm) films were mixed by 300 keV Xv' ions The resistivity of the mixing region was I )and to change drastically at the dose of 7xI0r° Xe'/cm`. When the test pie cracked under tension, the gauge measured the crack length with good accuracy. 1. Introduction Ion heart . mixing, which utilizes the kinetic energy of ions to mix predeposited surface layers with substrate matzrials, ha:" greatly expanded the potential uses of ion beams to modify materi;Is properties [1,2]. Recently, this technique has been applied to metal-insula'or systems where interest has focused on the finding that ion bombardment often increases the adhesion of the film to the substrate and the resistivity at the ion mixed region [3-5]. It is also possible to create lecar ized mixing products by ion bombardment with a micro-ion beam or an ion beam through a mask [6]. 'Me have undertaken the present investigation tct verify that an insulator/ conductor array can be formed in a metal- insulator system by bombarding with ion beams through the mask The technique was applied to construct a crack gauge which was attached to a compact tension (CT) test piece . An ordinary crack gauge with metal-insulator array formed on insulator substrate is attached to a test piece by an adhesion method. The crack length can be measured with the use of the resistance change caused by cutting of an array . However, the adhesion of the gauge under high-temperature (above 200°C) or wet conditions is apt tc be destioyed. and the reliabi!ity of the gauge being used tinder !hcsc conditions is low. The present m ".thod provides us a means of constructing a crack gauge . 2. Construction of the gauge The principle c( the crack gauge is based on the change of composite resistance of conductor/ insulator
hands induced by cutting of the bands by crack growth . Resistance increases stepwise only when _,onductor bands arc cut. The crack length can be derived from the number of steps caused in the gauge . The concentration of the crack gauge developed by the ton beam mixing technique is illustrated in fig . l . i n order to fabricate the crack gauge, at first, an insulator film was deposited by electr^n-!-2am evaporation on the CT test piece. Subsequently, a conductor film was deposited onto the insulator 1 11 im . : h,afiy, the spe,imens thus formed were irradiated through the mask with a .:et of aligned slits to form an array of insulator,/ conductor bands on th^ test piece . The bornbar6cd region was ion-mixed at,d this resulted in a rcsistl"ity increase. For insulator film SiO, was used, and Ru was the conductor film because their mixed products were expected to be a good insulator. Prior to forming the insulator/ conductor array, irradiation conditions such as ion dose to alter the mixed region into insulator were determined by measuring the resistivity of the mi. - pd r gion . A thin multilayered sample was used for this i,zr,lsuremcnt . It had 5 nm Si, 50 nm Ru and 30 nm Si layers deposited on a single crystal of Si on which the surface had been oxidized. The ovide laver was Ski, with a thickness of 300 nm. A Si layer was kept between SiO, and Ru layers in order to avoid their mixing by th^, rmal diffusion (see fig . 2) . This sample is called the Si/Ru/Si/SiO, sample in the following . Ion-beam-induced mixing was carried out by irradiation of 300 keV Xe' ions at 300 K vvith doses ranging from 0 to f; x 10" Xe'/cm` .'Thc Xc' current density was 2.2x lO t ' Xe'/cm = s in all cases . The in-sits observation of resistivity under irradiation was per-
0168-583X/93/$06 .00 C 1993 - Elsevier Science Publishers B .V. All rights reserved
S Ohno et ai. ! Dt Llptnew osa crackgauge by using ion beam tnixmg
Fi1;. 1 . Ct-,t - action
1309
precedure of the crack gauge attached to the C- 1' test piece by using 4,1 ion beam mixing technique .
formed by using a conventionally aligned four-point probe method . Synchronously with the resistivity measurement, RBS analysis of the Si/Ru/Si /Si02 sample was performed at cacti dose to determine the depth profile . To verify the formation of the insulator/ conductor array, the Si/Ru/Si/SiO, was irradi.rtcd through a mask with a set of slits of 0 .1 mm width . ï'he separation among the slits was 0.1 mm, as shown in 1. 3. Results and discussion
Si/Ray/Si sample increased with dose until 5 x lo t s Xe + /cm 2 , and saturated at a value of 6 .5 x 10 -4 S1 CM . RBS analysis was done for th,- Sa/Ru/Si sample irradiated with doses of 0, 1 X 10 15 and 1 .2 X 10 16 Xe }/cm= . These results are shown in fig. 5 . Above 5 X 10 15 X, `/cm 2, the composition of the mixed layer was approximatoly found to be Ru 2 Si 3. Ru-silicide (Ru 2 Si ;) ;vas produced by mixing of Si and Ru. Its resistivity was a f;vr time " la-ger than that of Ru, and the resistivity did got increase significantly if no oxygen was present in the mixed region .
3.1 . Resistivity change Resistivity data as a function of dose arc plotted it fig. 2 . The resistivity slowly increased with dose up to 7 X 10 1" Xc + /cn12 . Above this valu,-, the resistivity incrcase .i drastically to 0 .05 11 cm, and then tended 1o bt saturated . Results of RBS analysis of irradiated Si/Ru/Si/SiO, samples are shown in fig. 3 . The doses of two analyzedpoints ((1) and (2) in fig. 3) correspond to 2 X 10 1" and 7 X 10 1 ° Xe + /cm 2 , respectively . The mixed region appeared it , both cases and mixing progressed with increasing dose. Above 7 X 1016 Xc + /cm2 , the mixed region had an approximate composition of RuSi0- It is significant that the amount of oxygen diffusing towards the surfat,, increased with done . To investigate the reason why the resistivity of the mudd rt" vion increased in the case of the Si/Ru/St/SiO, sample, the resistivity change by ionbombartlment was measured with a reference sample, which is called the Si/Ru/Si sample in the following and consisted of 5 nm Si, end 50 not Ru layers on a Si wafer substrate . This rest,it is plotted in fig . 4. Irradiation conditions were the ,?me as those for the Si/Ru/Si/SiO, sample . T:te resistivity of the
(X10-2 ) 7
I-
EU C
i 5~ 4
r
3uoäcv xc Sv 5nm Ru 50cm _
Si :80nm
_, ~ 3Ô0 nm semplc Si/Ru/ .i/Si02 .
0
L
0
j - -7=__' __ _L _
3
Dise
4
5
6 (Xe+/cm 2)
7
8
1
9 (X1016 )
Fig. 2. Resistivity change of the Si/Ru/S'/S'()2 sample during irradiation with 300 keV Xe + ions at a current density of 2.2X 10 13 Xe + /cm 2 s. (1) and (2) show RBS-analyzed points ccrre~ponding to 2X 10 16 and 7.2X 1111^ Xz'/cm2 , respectively . Va . NOVEL TECHNIQUES (a)
1310
S. Oh- er ct / ()-rlnnmem ,,f a rraek Dose :
2.OX10' b
(Xe+ /cm Z )
garrge by a fing iori bemn rnWng
(1) Dose -~ 100
:
0
(Xe'/cm')
t
50
_v
U
Bv
0L
0
~i 20
11 40
60
80
100
12U
~2) Dose - 1 .0X10' 5 ();e~/(:m Z) 100--- ~-_ -
0
20
40
60
20
100
ï20
100
120
D,se
100-
C O '7t)
73
C
d U C O
U
U 0i
~_ .
J
50
----_--------i
20
-i0
60
80
Depth (nm) Fig . 3. RBS analysis of Si/Ru/Si/ SiOO Z sample with doses of 2x 1016 (1) and 7.2 x 10 16 Xe'/cmZ (2).
Depth (nn-.) Fig . i . RBS analysis of Si/Ru/Si san!ple with doses of 0 (1), I x 10 'S (2) and 1 .2x 10 16 (3) Xe`/cm' . The pieseure in the target chamber during irradiation was 7.2X 10 " Tui r . Os;gen could not be detected by RBS analysis.
From these re-~:ts, the large increase of resis?^ ,tt:,, in the case of the Si/RU/Si/S'02 sample was expected to be caused by production and thickening of
an insulating layer (SiRx'OZ ) by ditfusion of oxygen from die S'OZ layer into the Ru layer caused by ion mimag . Consùquently, liw cGndductuf layer became
0
40
80
120
160
200
240
280
(X10 -4 ', 9 r-
Fig. 4. Resistivity change of Si/Ru/Si sample during irradia tion with 300 keV Xe' ions at .a current density of 2 .2x 10" Xe'/cm Z s . (1), (21 and (3) show RBS-analyzed points corresponding to 0, 1 Y 10' s and 1 .2x 10 16 Xe `/cmZ, respectively.
Fig, 6 . Result of EPMA analysis for Si/Ru/Si/S'O Z sample irradiated with 300 keV Xe' through a metallic mask with a set of slits of 0.1 mm width after the Ru layer was removed by polishing . The achieved dose was 7 .OX 10 16 Xe'/cmZ . The signal of Ru was detected only in the mixed region .
S Orno er vl. / Develop-
1- .6
m
s
Cracklent t `i 0.1 Iw0.3 0.5
cf a c, ark gauge by using tonlearn mixing
(mm)
0.7
Crack ler_ ch 0.3 0.5 0.20 0'1
am
19.4
F-
Û
Û N ô d
V
mc
É
.f
V d N C N N
.N tr
0
50
1311
100
E.
F
0 .0~
(mm)
0.7 (b,
I
1
0
100
50
Cu-um time (see)
150
150
Cutting time (sec) Fig. 7. (a) The observed resis ante change of a crack gauge (eompostd resistance of all insulator/conductor band.) with crack growth. The resistance wa , measured with a constant current of 0.1 A . (b) The differential of the resistance change of (a) . thinner with increasing dose. It was deauced that the resistivity ~apid :y increased, because the resistivity is inversely proportional to the conductor layer thickness. This is still being investigated in more detail .
n w, t . was obtained front the number of bands. From th Esc results, it was concluded that bands were cut in acc,irdance with the crack growth.
3.2. Test pe "forrnance
4. Conci .lsiop
The Si/Ru/Si/Si0 2 sample was irradiated with 300 kcV Xe + through a metallic mask . The achieved dose was 7 x 10 1" Ae + /cm 2 . Fig . 6 shows the results of EPMA analysis for the irradiated sample after the Ru layer was removed by polishing . The signal of Ru was detected only in the mixed region . From this, it was confirmed that spreading of a narrow mixed layer outside the irradiated area did not c.;-ir . The width of the band was 0 .1 mm. The sample with a conductor/ insulator pattern .v w, cut in the direction perpendicularly to the band . The observed resistance change with progressing array cutting is shown to fig . 7a. Resistance was measured with a constant cur "eut of 0.1 A. The differential of the curve is depicted in fig. 7b. The e ;tcep peaks in fig. 7b correspond to the full cutting of one conductive band, From these results, it was thought to be possible to measure t6, crack length with an accuracy of 0 .2 mm (the sum of an insula,or and conductor band width) by using the insulator/ conductor pattern formed by ion beam mixing. Fig. 8 is a SEM observation of the crack gauge, which was formed by using ion beam mixing, and attached to the CT test piece, which was cracked under tension . The crack length was derived from the number of bands that were cut . After that, thin films consisting of Si/Ru/Si/Si02 layers were removed by polishing . The length in the test piece was measured by SEM observation. This value coincided with the crack length
A crack gauge was produced by using an ion beam mixing technique . The gauge consists of insulator/ conductor bands in an array on an insulator film attached to a CT test piece . The following results were obtained; 1) At a dose of 7 x 10 16 Xe `/cm 2, the resistivity of the mul,ilayered sample with Si/Ru/Si/Si02 layers increased rapidly. The resistivity increase resulted in
mixed region non-irradiatied region
100Nm
Fig. 8 . SEM observation of insulator/comiuctoi bands of the crack. gauge on the CT test piece aft^r introduction of a fatigue crack. Va. NOVEL TECHNIQUES (a)
1312
S Ohno er al. / D-. r,pmen , of a crackgauge
thickening of the insulator layer with increasing dose . This insulator layer was produced by diffusion of oxygen into the conductor layer. The rapid increase of resistivity was due to the fact that the rcsi " +ivity is ... __ .heck inversely .~ ~, proportional . ' ... . . ... ..,.. to tire Cî~ïejia .tvï lay .m ua.nlïSS .
2) An insulator/conductor array with spacing of 0.1 mm was form,,..d by using the ion beam nixing technique. 3) It was verified that the crack length was treasured by the gauge attached to the CT te"t piece with good accuracy .
by using ion
beam , ruing
References [Il F.W. S" aris, C .J. Mcliargue, R. K, .,sowsky and W.O. Hofer, .',,,pl . Sei . 1T, (1989) 103. [2] R.P. De Avillez, LA. Clevenger and C.V . 'rompsort, J. Mater . Re~. 5 (1990) 593. [31 X.X. Xl, Nucl. Instr. a^d Meth. B30 (1988) i6 . [41 A Perez, E. Ah-neau, G t uchs and M. Treilleux, Nucl Instr . and Meth . BCî (1-192) 129. [5l J.E.E. Baglin, Nuci. lnçtr . anu Meth . B65 (199D 119, [61 R.E . Beneson and P. Berning ';ilcl . Inst -. and Meth. B45 (19911) 519.