Ti-Si-C thin films with varying Si content between 0 to 10 at.% were deposited by DC magnetron sputtering from elemental targets. The effects on microstructure and lattice parameters were investigated using x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy, and first-principles calculations. The results show that the growth of pure TiCx onto Al2O3(0001) substrates at a temperature of 350 degrees C yields (111) epitaxial and understoichiometric films with x similar to 0.7. For Si contents up to 4 at.%, the TiCx epitaxy is retained locally. Si starts to segregate out from the TiCx to column boundaries at concentrations between 1 and 4 at.%, and causes a transition from epitaxial to polycrystalline growth above 4 at.%. Eventually, the top part of the films form a nanocomposite of crystalline TiC grains surrounded by amorphous SiC and C for Si contents studied up to 10 at.%. The results show that Si takes the place of carbon when incorporated in the TiC lattice.

We use transmission electron microscopy (TEM) for in-situ studies of electronbeam-induced crystallization behavior in thin films of amorphous transition metal silicon carbides based on Zr (group 4 element) and Nb (group 5). Higher silicon content stabilized the amorphous structure while no effects of carbon were detected. Films with Nb start to crystallize at lower electron doses than Zr-containing ones. During the crystallization equiaxed MeC grains are formed in all samples with larger grains for Zr (~5nm) compared to Nb (~2nm). Eventually the sample stabilizes and the crystallization process stops. A model is presented where the metal carbide grains nucleate and grow while Si segregates into the remaining amorphous matrix. At a certain Si concentration in the matrix the graingrowth stops.

Nanocomposite Nb-C coatings, with a C/Nb ratio of 0.93-1.59, have been deposited by reactive sputtering in a commercial sputtering system where the C is supplied from an acetylene gas at deposition rates of up to 200 nm/min. The coatings are compared to non-reactively sputtered Nb-C coatings deposited from Nb and C targets in lab-scale equipment at deposition rates two orders of magnitude lower. X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy are used to conclude that all coatings consist of nanoctystalline Nbc(x) grains (nc-NbCx) embedded in a matrix of amorphous C (a-C). The coating performance was evaluated in terms of their mechanical, tribological, and electrical properties. The chemical stability of the coatings was evaluated by exposure to a flowing mixture of corrosive gases. It is found that the coatings have comparable microstructure and performance to the coatings deposited by non-reactive sputtering. The high deposition rate and presence of different C-radicals on the coating surface during film growth for the reactively sputtered coatings are believed to result in a smaller NbCx grain size compared to the non-reactively sputtered coatings (reactive process: 10-3 nm, non-reactive process: similar to 75-3 nm). This difference results in a thinner a-C matrix of about 0.2 nm, which is not varying with C content for the reactively sputtered coatings. The thinner a-C matrix is reflected in coating properties, with a higher conductivity and slightly higher hardness. The coating richest in C content (C/Nb ratio 1.59) shows the lowest friction (0.23), wear rate (0.17 x 10(-6) mm(3)/mN), and contact resistance before (11 m Omega at 10 N) and after (30 m Omega at 10 N) the chemical stability test. These results imply that nc-NbCx/a-C coatings of this composition are a good candidate for electrical contact applications, and that up-scaling of the process is achievable.

Nb-Ge-C nanocomposite thin films were deposited by dc magnetron sputtering using three elemental targets. The films consist of substoichiometric NbC_x in a nanometer-thick matrix of amorphous C and Ge. Films with no Ge contain grains that are elongated in the growth direction with a (111) preferred crystallographic orientation. With the addition of ∼12 at. % Ge, the grains are more equiaxed and exhibit a more random orientation. At even higher Ge contents, the structure also becomes denser. The porous structure of the low Ge content films result in O uptake from the ambient. With higher C content in the films both the amount of amorphous C and C/Nb-ratio increases. The contact resistance was measured by four-point technique as a function of contact force between 0 and 10 N. The lowest contact resistance (1.7 mΩ) is obtained at 10 N. The resistivity varies between 470 and 1700 μΩ·cm depending on porosity and O content.

We report that an electron beam focused for high-resolution imaging rapidly initiates observable crystallization of amorphous Me-Si-C films. For 200-keV electron irradiation of Nb-Si-C and Zr-Si-C films, crystallization is observed at doses of similar to 2.8 x 10(9) and similar to 4.7 x 10(9) e(-)/nm(2), respectively. The crystallization process is driven by atomic displacement events, rather than heating from the electron beam as in situ annealing (400-600 degrees C) retains the amorphous state. Our findings demand a critical analysis of alleged amorphous and nanocrystalline ceramics including reassessing previous reports on nanocrystalline Me-Si-C films for possible electron-beam-induced crystallization effects.

Two series of Nb–Si–C thin films of different composition have been deposited using DC magnetron sputtering. In the first series the carbon content was kept at about 55 at.% while the Si/Nb ratio was varied and in the second series the C/Nb ratio was varied instead while the Si content was kept at about 45 at.%. The microstructure is strongly dependent on Si content and Nb–Si–C films containing more than 25 at.% Si exhibit an amorphous structure as determined by X-ray diffraction. Transmission electron microscopy, however, induces crystallisation during analysis, thus obstructing a more detailed analysis of the amorphous structure. X-ray photo-electron spectroscopy suggests that the amorphous films consist of a mixture of chemical bonds such as Nb–Si, Nb–C, and Si–C. The addition of Si results in a hardness decrease from 22 GPa for the binary Nb–C film to 18 – 19 GPa for the Si-containing films, while film resistivity increases from 211 μΩcm to 3215 μΩcm. Comparison with recently published results on DC magnetron sputtered Zr–Si–C films, deposited in the same system using the same Ar-plasma pressure, bias, and a slightly lower substrate temperature (300 °C instead of 350 °C), shows that hardness is primarily dependent on the amount of Si–C bonds rather than type of transition metal. The reduced elastic modulus on the other hand shows a dependency on the type of transition metal for the films. These trends for the mechanical properties suggest that high wear resistant (high H/E and H³/E² ratio) Me–Si–C films can be achieved by appropriate choice of film composition and transition metal.

DC magnetron sputtered Ti-Si-C thin films with varying Si content between 0 to 13 at.% were deposited from elemental targets. The effects on microstructure were investigated using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Results show that the growth of pure TiC_x onto Al₂O₃(0001) at a temperature of 350 °C is epitaxial and understoichiometric with x~0.7. For Si contents up to 5 at.%, the Si is incorporated into the TiC_x with retained epitaxy. For Si contents above 5 at.%, the Si segregate out from the TiC_x to the grain boundaries forming, causing a transition from of epitaxial to polycrystalline and nanocomposite growth.

A method based on focused ion beam milling and analytical electron microscopy to investigate the nature of the tool-chip interface is presented. It is employed to study tool-chip interfaces of the rake face of a (Ti0.83Si0.17)N coated PCBN insert after turning of case-hardened steel. Analytical electron microscopy shows the presence of a smeared adhered layer on the coating, which consists of steel elements from the work-piece, oxygen, and Si and N, most likely originating from the coating.

(Ti1-xSix)N-y (0 andlt;= x andlt;= 0.20; 0.99 andlt;= y(x) andlt;= 1.13) thin films deposited by arc evaporation have been investigated by analytical transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and nanoindentation. Films with x andlt;= 0.09 are single-phase cubic (Ti,Si)N solid solutions with a dense columnar microstructure. Films with x andgt; 0.09 haven a featherlike microstructure consisting of cubic TiN:Si nanocrystallite bundles separated by metastable SiNz with coherent-to-semicoherent interfaces and a dislocation density of as much as 10(14) cm(-2) is present. The films exhibit retained composition and hardness between 31 and 42 GPa in annealing experiments to 1000 degrees C due to segregation of SiN, to the grain boundaries. During annealing at 1100-1200 degrees C, this tissue phase thickens and transforms to amorphous SiNz. At the same time, Si and N diffuse out of the films via the grain boundaries and TiN recrystallize.

Utvecklingen inom materialforskningen går mot att framställa avancerade material vilka är skräddarsydda för olika tillämpningar. Detta har medfört att det blir allt mer populärt att belägga ytor med ett eller flera tunna lager med syfte att förbättra materialegenskaperna. Användningsområden för ytbeläggningar går att hitta inom allt från vardagliga produkter såsom teflonbeläggningar av stekpannor, förgyllning av smycken till avancerad halvledarteknik för att åstadkomma energieffektiva lysdioder. Det enskilt största tillämpningsområdet för tunna filmer är dock som skyddande skikt för verktyg inom skärande bearbetning. Utvecklingen går stadigt mot högre skärhastigheter och därmed ökade temperaturer, idagsläget kan området där verktyget och arbetsmaterialet är i kontakt nå temperaturer på mellan 800-1000 °C utan att förlora nämnvärt i styrka. Detta har gjorts möjligt genom att belägga skären med någon eller några μm (tusendels mm) av lämpligt keramiskt material i avseende att öka motståndskraften för nötning vid bearbetning vid höga temperaturer.

I den här avhandlingen har tunna filmer studerats med det övergripande målet att förbättra egenskaper hos verktyg för skärande metallbearbetning genom att öka motståndskraften hos materialen mot mekanisk och kemisk nötning vid höga temperaturer. Materialsystemet som undersökts är Ti-Si-N, där tunna filmer av både legeringar och tvåfassystem har syntetiserats och egenskapskarakteriserats. Legeringarna är belagda med varierande Si-halt från 0 till 10 atomprocent och avsedda för att studera strukturella, termiska och mekaniska egenskaper. De framställdes med en teknik som kallas arcförångning, där man i ett vakuumsystem frigör högenergetiskt material i det här fallet av Ti och Si som förångas från en solid yta kallad target. Atomerna joniseras genom kollisioner med elektroner och reagerar på sin väg mot substratet med kvävgas. Väl framme vid substratet, kondenserar jonerna och bilder den tunna filmen. Filmerna består av två strukturtyper, den första är en fast lösning där Si atomer upp till 5 at.% ersätter Ti atomer i TiN. I det andra fallet så segregerar Si till korngränserna. Värmebehandlingsexperiment visar att Si bildar SiNx som kapslar in TiN-korn vid temperaturer upp till 1000 °C. Hårdhetstester visar att filmerna bibehåller sin hårdhet upp till 1000 °C tack vare fasomvandlingen. Även vid 1100 °C är hårdheten hög. Dessa skikt besitter alltså egenskaper som gör dem väldigt användbara inom tillämpningar för skärande bearbetning.

Nanostrukturerade materials egenskaper beror på dess mikrostruktur snarare än på de grundämnen som ingår, detta exemplifieras av TiN-SiNx-nanokompositer bestående av nanokristallina TiN-korn inbäddade i några få atomlager SiNx, där materialegenskaperna helt och hållet beror på kornstorleken på TiN-kornen och tjockleken på SiNx-lagren. Ökas tjockleken på SiNx minskar hårdheten. Dessa filmer har mycket goda mekaniska egenskaper och är ett av de hårdaste materialen som finns. Nyckeln till den höga hårdheten hos skikten ligger i att bilda starka bindningar mellan TiN och SiNx. Hur dessa ser ut vet man dock inte eftersom strukturen på SiNx gränsytan inte är känd. Anledningen är att den är svår att avbilda på grund av dess krökta form och begränsade volym. I denna avhandling har TiN/SiNx multilager belagts, dvs. en lagrad struktur TiN alternerad med SiNx. Dessa filmer framställdes med sputtring, en teknik som liknar arcförångning men där man istället accelerera positivt laddade joner mot Ti och Si targets med en hög negativ potential som frigör Ti och Si. I multilagren varierades SiNx-lagrets tjocklek mellan endast några få atomlager för att göra en förenklad modell av gränsytan hos nanokompositen och med atomupplöst transmissionselektronmikroskopi samt hårdhetsmätningar konstateras sedan att de hårdaste filmerna var de där kristallin SiNx stabiliseras mellan TiNkorn. Vidare studerar jag SiNx/TiN ytor med sveptunnelmikroskopi och täthetsfunktionalteori (en kvantmekanisk simuleringsmetod). Mina resultat visar SiNx och bindningarna till TiN är mycket mer komplicerade än vad man tidigare trott, då de kan vara kristallina och anta komplexa rekonstruktioner. Detta bidrar till den starka bindningen mellan TiN och SiNx vilket i sin tur förklarar varför materialen blir så hårda.

Ti-Si-N and Ti-Al-Si-N thin solid films have been studied by analytical electron microscopy, X-ray diffraction, scanning tunneling microscopy, X-ray photoelectron spectroscopy, elastic recoil detection analysis, nanoindentation, and ab initio calculations. I find that arc evaporated (Ti1-xSix)Ny films can be grown as cubic solid solutions up to x = 0.09 with a dense columnar microstructure. Films with higher Si content up to x = 0.20 assumes an extremely defect-rich, feather-like structure consisting of cubic TiN:Si nanocrystallite bundles with low-angle grain boundaries caused by thermodynamically driven Si segregation. Correspondingly, the N content in the films increases close to linear with the Si content from y = 1.00 (x = 0) to y = 1.13 (x = 0.20). Annealing of the films at 1000 °C yields a metastable crystalline SiN_z (1.0 ≤ z ≤ 1.33) tissue phase in 0.04 ≤ x ≤ 0.20 films which is (semi)-coherent to TiN. These films are compositionally stable and exhibit retained hardness between 31-42 GPa up to 1000 °C. At 1100-1200 °C, the tissue phase amorphizes and all SiNz diffuse out of the films, followed by recrystallization of the cubic phase. Hard turning testing was performed on (Ti_0.83Si_0.17)N1.09. Analysis of the tool-chip interface prepared by focused ion beam revealed shear deformation in the film and an adhering layer consisting of the work-piece material and Si and N from the film. For (Ti_0.33Al0.67)_1-xSi_x)N (0 ≤ x ≤ 0.29) films the NaCl structure cubic (Ti,Al)N solid solution phase is predominant at low Si contents, which gradually changes to a dominating hexagonal wurtzite (Al,Ti,Si)N solid solution for 0.04 ≤ x ≤ 0.17. Additional Si results in amorphization. Annealing experiments at 600-1000 °C yields spinodal decomposition of c-(Al,Ti)N into c-AlN and c-TiN, with corresponding age hardening. The h-(Al,Ti,Si)N films exhibit precipitation of c- TiN with smaller volume than the host lattice, which results in tensile cracks formations and age hardening. Films with c-(Ti,Al)N perform best in turning applications, while films with h- (Al,Ti,Si)N form cracks and fail. Finally, I have characterized the nature of metastable crystalline SiN_z phases and the interface between TiN(001) and SiN_z. Magnetron sputtering was used to deposit TiN/SiN_z(001) nanolaminate films with varying SiN_z and TiN layer thicknesses. Maximum hardness is obtained when SiN_z forms coherent interfaces with TiN. In addition, in situ surface analyses in combination with ab-initio calculations reveal that SiN_z sub-monolayers grow epitaxially and form crystalline reconstructions on TiN(001) and TiN(111) surfaces. Phonon calculations predict that stoichiometric c-SiN is dynamically instable when the atoms are arranged in the NaCl and ZnS forms. However, c-Si₃N₄ can be stabilized with D₀₂₂ or L12 ordered ZnS-like structures. These results have impact for the design of superhard nanocomposites and multilayer thin films.