* . . . . . M 7 I " . ) : ! . UNCLASSIFIED ORNL 193 M di 57 - - - - - . - ..::-. -.- - . -.-- .** . -. .' . - - - ..* * 1. - ... *** . .- . Orne-p-193 : THE AUG 1 3 1964 Agus 1 3 1964 64-48 CONF-kost To be published in: Proceedings of ASTM Conf. held June 7-12, 1964, Montreal, Canada. MASS SPECTROMETRIC STUDIES OF SPIRED PARTICLES FROM COPPER PONOCRYSTALS* A. L. Southern Solid State Division, Oak udge llational Laboratory Oak Ridge, Tennessee As a part of a program for studying the sputtering from the sw•face of copper mono- crystals bombarded with positive argoni Cons, the pe, intersity, and energy of the sputtered particles is being investimented witr a high-vacuum mass spectrometer. The results of some studies to determine cechniques for obtaining clean surfaces are re- ported here, and some of the proper cirs of the copper ions sputtered Dj 2.5 kev argon ions are described. The cual-beam mass spectrometer sed in this study has been described by the malucturer. Therefore, only a cia pat the bombarding ion source and the location of the soiid angle for sputtered irricles is 32.00 in Fig. 1. The target could be rotated so as to obtair an angle o ncidence or to 900 for the socioarding ion beams and the particles sputtered at a b le 900 tone incidence ion beam were mass analyzeà. This arrangement allowed only the putered articles to be analyzed ice all a igles ca incidence, except for 450, for which both sputtered and reflected particles were ana- lyzed The target could be heated to aproximately gocºc by electron boardment on the target holder and the temperature could be morritored with a piatinut-pistin raodimo thermocouple or by optical methods. The complete spectrometer could be baked out at 400°C by an oven. The best backgrow. i presse, obtaired was 1 x 10-9 tor, but pressures were generally in the range 3 x 10-4 to i xicot torr. Typical pressures in the syster during operation were 2 x 10-6 torr in. -.e source, 3 x 10°! in the target region, and ? x 15°8 in the mass analyzer. The maximu. bonca ding Art ion current dersi:y was ? val C.? ał 3 kev energy and the minimum. araiyzer current measurable was 5 % 10-19 ampere. The copper tar gets used in these experiments were sliced from a crystal with (200) surfaces by an acid saw (Fig. 2). Her tar det å was rotated in the mass spectrometer the directions of incidence of the argon ion beam were in the 100 29.72 a. or arget 3, the [110] zone. The (100) surfaces were chemically lapped, electropoiisted and washed to obtain a lat clean surface. The degree of surface cleanliness was evaluated by comparing tar opecira ci tre ejected positive ions. Table I shows the relative intensities of the positive 100.5 ejected from the copper surface after various conditions of heat treatment. The in- tensities were normalized to más 63 7the initial run, which was made :rom a targe: cieaned by electropolishing. The degree co cleaniiness was Cound to be cest after one syster bake-out at 400°C and two target bake-outs at 600°c. System inake-outs appeared to drive impurities to the crystal currace, while bake-out of only the crystai removed these impurities. The In* was 12 in india contamination in the system. arii could easily be removed by tar det bake-out. Ise decrease ir intensities on we cooper ions wita bake-out cannot be expiained by a crange in cleanliness. Ion creadme..i of the surface should serve to clean the homearded area, but ine peak intensiiies ning any ore experiment were essentially consi2nt, his), note that com as 2032 it :03 ail cases. The recording of the peaks olcü' ana o target for a: a.ie incidence om COO is shown in Fig. 3. Figures - 55.00 relative peak heights 2..d area under the bilo praks is. &azie of incidence : 32 tar et å ará 3, respectively. The resulis :ro- Parents to 32,0 ai'e cuestionable since for tese ar.des the target surface coi intercept tác convicte team. The peak widths at alf reignt othe 650.11 and 53 sputtere: iron target fo are shown in Fig. 6. As can be see:. zor angies of incidence Q Less ta.. about ECO tie reis overlapped so much that in:icmation on the separate peaks oma..ot be o. ta'neri. Kail, 23 an be seen from Figs. poá, inc ratio of peak heights o: 986 23 cm are equal the isotopic ratio for coming a soli raage of $ for target 1720-600); Reseaza sponsored by the U. S. Atomic Energy Commission inter contrui més este Unica: "iroido Corporation. LEGAL NOTICE -- andra - - i . . TE . . * > ne voli ior target 3. (As described above, only ionu cjected 90° to t!i unele or incidu.co une collected.) Pea: helgii 18 pro;»93'tlonul to intens!ty on.y if (2) "he perks aro separated, and (2) peak widlins are either independent of or directly proportional to Q. fir tarse a cullit!on (1) is met 0 for $72°, ani sinc! the ratio is not correct :'or > S., must be concluded tincidunt condition (2) 16 110t true. Thereforc, uny addico- meilt in t'iese experiments between tie ratios of the peak heights and the 180topic ratio 18 roztuitous. from Figs. hot and 5 it is clear wat irc inte.isity of Cu ions ejeitce varies with , god in a very complicated way (Omiy ion Preater than 70° are the reass for oscut and 03cu' 3uriciently separated to allow the arcus wider the individual peaks to be ob- talaed.) With increasing the arcı kinder the peaks increases for target A and decreases for target B, though not monotonically in either case. Since the intensity is maxinun for target A at Q 450, direction or incidence and direction of ejection both (oll), and for target B at 90°, direction of incidence approaching (110 and direction of ejection [001] , it can be conciuded tht the intensity o. ions 18 gentest when a [110] is involved, as hagi been shown i'or atoms cjected in sputtering. It appears thut there may be sane correlation between the other vunps in the area vs. $ curves and crystallo- D'aphic directions, but if 50, it is not thought to be significant at this time. Calculations based on the Langnuir-Suha formula o: the ratio of sputtereà ions to scuttered neutrals seem always to be smaller thari experimental estimates. Using a value for the sputtering yieli of 4 atoms/ion, the ratio of sputtered ions to sputtered neutrals was estimated to be about 10-7, while this ratio predicted from the Langmuir- Saha formula was about 10-54. ererences 2. A. J. Smitti, L. A. Cambey, and D. J. Marshall, J. Appl. Phys. 34, 3489 (1963). 2. I. Langmuir and K. H. Kingdon, Proc. Roy. Soc. (London) 207, 61 (1925). 3. A. I. Southern, William R. Willis, and Mark T. Robinson, J. Appl. Phys. 34, 153 (1963). UNCL ASSIS1CD ORNL OWO. MASR TABLE I. POSITIVE IONS EJECTED FROM A (100) COPPER MONOCRYSTAL BY BOMBARDING WITH 3 kov Ar' IONS AT AN ANGLE OF INCIDENCE OF 75° MASS PROBABLE IDENTIFICATION INITIAL RUN RELATIVE INTENSITIES SYSTEM 1st TARGET BAKE-OUT BAKE-OUT 2nd TARGET BAKE-OUT Ayx Ż 13 xx Ù ¿ 3's O--ūna 400 3 17 3 UNCLASSIFIED ORNL-OWG 63-2220 GAS INLET - FILAMENT MAGNET BOMBARDING ION BEAM DEFINING SLITS TO MASS ANALYZER - SPUTTERED PARTICLES 90° FROM BOMBARDING ION BEAM TARGET ROTATES ABOUT CENTER LINE FROM O TO 90° WITH RESPECT TO THE BOMBARDING BEAM i Fig. 2. Schematic diagrain of the bonbarding ion beam, target and section of the sputtered particles analyzed. UNCI.ASSID110) ORNL --OWG 60-41261 TARGET "A" LE----- TARGET "8" -----> COPPER (100) 0, 0, A REFERS TO [100], [110] AND (141) DIRECTIONS RESPECTIVELY Fig. 2. Orientation of targets A and B. Fig. 3. Le- WAT wo ULT LUI V . F Qani u 1177 M - X - v * *- **- - nt. Fig. 3. 63 + Cu and Cu* sputtered from copper monocrystal with 2.5 kev Ar* ion bonbardinent at an angle of incidence of 80°. - 1 .1 Will . . den... Au. ' . . lib . - .............. - www.it should well. . . . ......... . .... . ......... UNCLASSIFIED ORNL-DWG 64-4514 . C T 1 CO PEAK HE'GHT (relative) AREA UNDER 63cut + 65 Cut PEAKS (relative) TARGET "A" 45 50 85 90 55 60 65 70 75 80 ANGLE OF INCIDENCE (deg) Fig. 4. Peak height and area under the peaks as a function of angle of incidence for 63cut and 65cu* sputtered from target A with 2.5 key Art ion bombardment. * . * * ... 12t: : . .. . . 4 .:. UNCLASSIFIED ORNL - DWG 64 -4513 AREA PEAK HEIGHT (relative) AREA UNDER 63 Cut + 69 Cut PEAKS (relative) 10 TARGET "B" 45 90 50 55 60 65 70 75 80 85 ANGLE OF INCIDENCE (deg) Fig. 5. Peak height and area under the peaks as a function of angle of incidence for 63Cut and 65Cut sputtered from target B with 2.5 kev Ar* ion bombardment. UNCLASSIFIFO ORNL-DWG 64-4428 PEAK WIDTH AT 50 % HEIGHT (ev) . 45 50 55 60 65 70 75 80 ANGLE OF INCIDENCE (deg) 85 90 Fig. 6. Peak width at 50% level as a function of angle of in- cidence for 53cut and oscut sputtered from target A with 2.5 kev Ar* ion bombardment. . . . . AN 27 0. 1 .III. DATE FILMED 11/23/64 - LEGAL NOTICE - This report w mopardd um account al Government sponsored warten Notthor the United Name, nor the Commission, nor any porn noting on whall of the Commination: A. 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