Chromium nitride films are known as good protective layers for against both corrosion and wear. These coatings have been studied in detail during recent years. Their protective capability strongly depends on the deposition conditions. A modern method for preparing chromium nitride is the IBAD (Ion Beam Assisted Deposition) method. The main parameter determining the composition and properties of the films prepared by the IBAD method is the arrival ratio of impinging nitrogen ions to chromium atoms. In order to calibrate the ion beam XY-mechanical scanner with a Faraday cup, a detector was designed and constructed. By mathematical processing of the data, the flux of the nitrogen atoms was found. To obtain the flux of the chromium atoms the RBS and Talystep methods were used. Now, on the basis of this data, we can perform CrNx, coatings with controlled composition and properties

Hüttel, I.

Konvičková, S.

Palamarchuk, D.

Zoriy, M.

Černý, F.

English

CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)

Acta Polytechnica Vol. 43 No. 112003Measuring the Process Parameters of theIBAD MethodM. Zoriy, F. iernf, D. Palamarchuk, S. Konvidkov|,l. HiittelChromi,um nitride flms are knoun as good protective layrs for against both corrosi,on and wear. These coatings haae been studied in denilduring recent years. Their protectiae capabilitl strongly depends on the deposition conditions. A modern method for preparing chromiumnitride is the IBAD (Ion Beam Assisted Deposition) method.The mrtin parameter deterrnining the compositi,on and properties of the f.lms prepared b1 the IBAD method is the arriaal ratio of impingingnitrogen ions to chromiunT atoms.In orfur to calibrate the ion beam XY-mechanical scanner uith a Faradal cup, a detector uas designed and consltucted. By mathematicalprocessing of the data, the flux of the nitrogen atorns was found. fo obtain the llux of the chromiuln atoms the RBS and Talystep methodsuere usea.Nou, on the basis of this d,ata, arc can perfonn CrN, coutings uith controLled composition and propeflies.Kelwords: IBAD, CrN, CrN2, calibration, eleclron beatn.1 IntroductionIn recent years the hard coatings have play a major role inmechanical engineering. Hard coatings are used to increaseresistance against wear and fatigue.Many kinds of hard coatings are now known. 'lhe mostwidely used is titanium nitride, because of its high hardness[]. Chromium nitride is used for the same pr<rpose [2].In addition to high hardness it has a very goocl corrosionresistance, especially under high temperatures in variousatmospheres. The hardness and friction properties of chrrcmi-um nitride coatings depend on the structute and orientationof the crystals in the film [3]. The corrosion properties alsodepend on the porosity/densitv of the coatings [4]. The im-portance of the deposition parameters is critical.There are many methods for preparing these coatings,which can be classified in various ways. Eflective modernmethods are based on plasma and ion beam processing tech-nology. One of these is the IBAD method [5].A schematic view of the experimental arrangement forthe IBAD method is shown in Fig l.RotaryIy'anipulatorlonSourcelon Beam Ni + N-It involves deposition of a desired material using a vac-uum electron beam evaporation technique and simultaneousbombardment by an energetic ion beam.Chromium nitride has nvo stoichiometric modifications -CrN and CrrN [6]. Howeveq wewill be preparing a customarycomposition CrN*, where x is in the range of [0+l], and wewill investigate the characteristics of the process in depend-ence on the x ratio. To do this, we need to calibrate the depo-sition subprocesses - the atomic fluxes of chromium andnitrogen in IBAD equipment.2 Calibration of an ion beamA flow of nitrogen of high purity is fed into the ion source,where ionization of the nitrogen takes place. The ion sourcewas developed from the Franks Jivin Anode design. It consistsof a graphite outer tubewith closed ends, mounted in an insu-lator. Inside the tube there are two tungsten electrodes, closelyspaced about the centerline ofthe tube.At a distance of 35 mm away, there is a correspondingwider slit in the extractor electrode. During operation a hightension of 90 keV is supplied to the ion source.The large potential diflerence between the positive HT inthe ion source and the zero voltage of the extractor electrodeprovides the force to accelerate the positive nitrogen ions toa high velocity and form the ion beam. Once the ions passthrough the slit in the extraction electrode they continue atconstant velocity until they hit the work piece. The ion beamis a mixture of molecular and atomic ions in proportion 3:1.As a goal we need to know the quantity of nitrogen atomsthat the sample per unit area per unit time - the flux of thenitrogen atoms. The TECVAC 221 Ion Implanter has nosuitable measuring instrument for this, so we made an appro-priate device ourselves and used it to perform the calibrationof the ion beam.c=-rEvapomted Crl: Schematic view of experimentalIBAD methodEleclronBeamFig. arrangement for the23Acta Polytechnica Vol. 43 No. l/2003This device is a mechanical XY-scanner that consists ofa Faraday cup detectoS nvo stepping-motors, a scrollingmechanism and other accessories.A program was written in C language to conrrol rwostepping-motors, which moved the detector into selectedpoints of cross-sections of the ion beam. An XY-scanner wasapplied in ttre region of dimensions 200 x 200 mm witha step of 2 mm. Another program estimated the value of ionbeam densiry and plotted the graph that illustrated the pro-file of ion beam density. The resulting distribution of ionbeam density in the TECVAC Ion Implanter is shown inFig. 2. This is the profile of the ion beam current density,but we need a profile of the flux of the nitrogen atoms.We therefore need to perform a mathematical procedure totransform ion beam density into atomic nitrogen flux. Wecalculated the quantity of nitrogen atoms as follows:So the fluxes of the atomic and molecular ions will be.respectively:^ P 6.2+2.tot3P* =i =14355'lol3 cm-2's-l;P2N = P - Px = 5.742' l0l3 - 1.4355' l013==4.3065.1013 cm-2.iIThe flux of the atoms included in the atomic nitrogen ionsequals the flux of the nitrogen ions:NN= PN = I.4355' i0r3 .--2',-';The flux of the atoms included in the molecular nitrogenions equals flux of equal rwice the flux of the molecular nitro-gen ions:Nr*= t'Pr"= 8.613'10t3 cm-2's-';So th. tot"ljq* of .tit-g.n utornr itln, =t"ll,rr =t.oou'rotn.--t ,i'l- total flux of nitrogen atoms.The Profile monitoring of the flux of aroms is shown inIig.3050X-axis [mm] o-so -so Y-axis [mm]Fig. 3: Profrle monitoring of total flux of nitrogen atomsAnother view of the same profile is presented in Frg. 4.This figure shows that the profile of the flux has its maximumin the ellipse region, extended along the X-axis.-60 so to y_axis [mm]Fig. 4: Profile monitoring of total flux of nitrogen atoms (anotherview)q.i- 12c'b 10=B50 50Y-diE mmXdinm.50 -50Fig. 2: Profile monitoring of total flux of ionsGiaen dnta:I =9.2 pNcm2 - example of value of ion beam density (mea-sured by Faraday cup detector);e = 1.6021892. l0-lsc - electron charge magnitude;P1g - flux of atomic nitrogen ions;P2^*' - flux of molecular nitrogen ions;P - total flux of ions;N1,'- flux of nitrogen atoms included in atomic nitrogen ions;N2.iy - flux of nitrogen atoms included in molecular nitrogenions;N - total flux of nitrogen atoms.Pr o cedur e for S ohrti,on :We know the ion beam density and charge of one ion.From this data we are able to calculate the total flux of ions:p =! =-g+rr =5.742' 1013 cm-2's-r - totul fl,,*e 1.60221892.10-rof ions;"'* =? - number of molecular ions: number of atomic ions:PNIP=Px,*Porr=) P =l+3=4.Py24EoaActa Polytechnica Vol. 43 No. 112003;E C(g='fi'oEI=(5E50E.9xI.oFig. 5 shows a view fiom below of the profile monitoring ofthe total flux of the nitrogen atoms, and gives more informa-tion about the distribution the flux in the cross-section of theion beam. Using this figure we can select a zone approxi-mately 50 mm long and 30 mm wide, where the flux of thenitrogen will vary within a range of 15Vo.-!o 30 o -30 -50Y-axis [mm]Fig. 5: Profile monitoring of total flux of nitrogen atoms, seenfrom belowSo if we locate our samples in this region we will achievesatisfactory homogeneity and will be able to control the quan-tity of the nitrogen atoms that arrive on a unit area Per onesecond.3 Calibration of the electron beamevaPoration systemTo check the composition of chromium nitride we alsoneed to calibrate the flux of the evaporated chromtum atoms.In the TECVAC Ion Implanter the evaporation is sup-plied by an electron beam grn. When the electron beam gunis running, it produces a powerful beam ofelectrons that areaccelerated by negative high-tension up to -10 kV This elec-tron beam melts and evaporates the chromium that depositson the sample.Besides depositing chromium on the sample that ismounted on the rotary manipulator, chromium is also depos-ited on the quartz crystal microbalance. This crystal oscillateswith an original frequency, of 5 MHz, and the frequency ofoscillation decreases with the mass of deposited chromium.In this way we can measure the thickness of the depositedcoatings.To check the measured thickness of the coatings, theThlystep m€thod was used. In this method, a thin needlemoves along the surface and detects the step between thesurface ofthe substrate and the surface ofthe coating. Thenthe value of this step is converted into an electrical signaland the thickness of the coating is displayed.To obtain the quantity of the chromium atoms in ourcoatings, the RBS (Rutherford Backscattering SpectroscoPy)method was used. Our samples were bombarded by alphaparticles with energy 2MeV. By measuring the energy ofthe backscattered particles the exact quantity of chromiumatoms was determined. Examples of the energetic spectraare shown in Fig. 6 and tig. 7.ki+ItBSAC.I.IIExp.7201(200 nm)oSif'\)\1 000200 400 600 800 1000 1200 1400Energy (keV)r600Fig 6: Sample 200 nm..2 MeV alpha particles. The quantity of Cratoms is 2.1 . I0"'cm-t.Exp.7204 (300 nm)Cr-tt\\IE(55bCAn -t-200 400 600 800 1000 1200 1400 1600Energy (keV)Fig. 7: Sample 300 nm, 2_MeV^alpha particles. The quantity of Craroms is 5.05. I0''cm-'.By comparing this data with the data measured by ourIBAD equipment we calibrated the electron beam evapora-tion system.For example, when the electron beam currentwas l00mA,the flux of the chromium atoms was 2'1013 at'cm-2.ConclusionsOur ultimate goal is to prePare coatings of chromiumnitride. To check the properties of these coatings we need tocalibrate the deposition subprocesses - the atomic fluxes ofchromium and nitrogen in the IBAD equipment. These cali-brations have been done.In order to calibrate the ion beam we designed andconstructed an XY-mechanical scanner with a Faraday cuPdetector. By mathematical processing of the data we foundthe flux of the nitrogen atoms.To obtain the flux of the chromium atoms we used theRBS and Talystep methods.25Acta Polytechnica Vol. 43 No. 112003Now, on the basis of this data, we can perform crN* coat- Doc. Ing. Frantisek ierny, csc.ings with controlled composirion and properties. phone: 1420 224 zbz $;7e-mail : cernyf@fsid.cvur.czAcknowledmentThis research has been supported by GACR grantNo. 106/02/1194 and conducted within the fiamework ofresearch project No. J04l98 : 2 I 00000 I 2.Referencestll Galvanetto, E., Galliano, F. P., Fossati, A., Borgioli, F.:Surf. Coat. Technol., Yol. 44,2002, p. 1593-lO0O.I2l Mernagh, V. A, Kelly, T. C., Ahern, M., Kennedy, A. D.,Adriansen, A P. M., Ramackers, P. P.J., McDonnel, L.,Kockoek, R.: Surf. Coat. Technol., Vol. 49, 1991, p. a62.t3l Smidt, F. A.: Int. Mater. Rev., Vol. 35, 1990, p. 61.t4l Kumar, S., Rajul, V. S., Arunachalam, J., Khanna, A.,Prasad, K.: Thin Solid Films, Vol. 388, 2001 , p. 195-200.t5l Pakala, M., Lin, R. Y.: Surf. Coat. Technol., Vol. 81,1996, p. 233-239.t6l Cunha, L., Andritschky, M., Rebouta, L., Pischow, K.:Surf'. Coat. Technol., Vol. I19, 1999, p. I152-l160.Ing. Miroslav Zoriye-mail: mzorij@seznam.czIng. Dmytro PalamarchukDepartment of PhysicsDoc. Ing. Svatava Konviikovd, CSc.phone: +420224 352 5lle-mail : konvicko@fsid.cvut.czDepartment of MechanicsCzech Technical University in PragueFaculty of Mechanical EngineeringTechnickii 4.166 07 Prague 6, Czech RepublicDoc. Ing. Ivan Htittel, CSc.phone: +420 224 353 205e-mail: huttel@vscht.czInstitute of Chemical TechnologyTechnickd 3,166 28 Prague 6, Czech Republic26

Measuring the Process Parameters of the IBAD Method

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Measuring the Process Parameters of the IBAD Method

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