Good quality p+/n and n+/p shallow junctions (< 0.15 um) with reverse current density of few nA/cm2 and low contact resistivity (∼ 5×10–7 Ω cm2) have been fabricated by using Mo suicide and Rapid Thermal Annealing (RTA). The processes of implantation through Mo films and into MoSi2 layers have been comparatively analysed on the basis of SIMS and carrier concentration profiles, TEM observations and DLTS measurements. In the case of n+/p diodes fabricated by ITM technology slightly worse leakage currents have been observed, in spite of the better planarity of the silicide-silicon interface exhibited by these structures.

Using ion implantation it is possible to induce a variety of phase transformations in the surfaces of stainless steels. The implanted layer can be either amorphized, undergo an fee (γ) => bec (α') martensitic transformation, or compounds can be formed between implanted atoms and target atoms. Stress provides a dominant contribution to the driving forces for amorphization and martensitic transformations. Implantation-induced alloying is important for obtaining the right composition in the implanted layer, whereby the transformation conditions can be optimized. Amorphization is best achieved by implantation of metalloids or other conventionally known glass forming elements. Martensitic transformations in austenitic steels are most easily induced after implantations with noble gases — including helium, where highly pressurized noble gas inclusions are formed. Implantations at high fluences with compound forming species such as nitrogen, boron or phosphorus, will often produce an implanted layer with a structure resembling a ceramic glazing which, depending on the implant species, will be amorphous or crystalline.

In order to understand and predict changes in the surface properties of implanted stainless steels, a detailed knowledge of the implantation induced microstructures is essential. The implanted surface will often have a multiphase structure giving only moderate improvements in corrosion properties, and in particular, resistance to pitting corrosion will often be reduced or only slightly improved. Surface hardness will, on the other hand, in many cases be increased, and large improvements will often be observed in wear and friction properties of the implanted surfaces. Under conditions where formation of a homogeneous surface layer is facilitated, the fatique life of implanted samples may also be extended.

Implantation of Ta into single crystal Ni3Al was conducted to determine whether this would be an effective means of producing surface hardening in monolithic alloys. Ta was implanted at 400 keV to doses of 0.7, 3.6 and 25.2 × 1015 cm2 along the <100> axis of a <100> crystal of Ni3A1 at room temperature. Composition vs depth profiles were determined by RBS and lattice location of Ta was determined by channeling angular yield scans about the <100> axis. The hardness of the surface was measured by ultra-low load indentation. Results show that implantation softens the surface and that the Ta is randomly distributed between Ni and A1 sites. Annealing at 1000°C/1h significantly reduces the damage and causes preferential occupation of A1 sites by Ta. It also results in a slight increase in surface hardness. Further annealing at 1200°C/0.25 h increases the surface hardness substantially. The results indicate that the as-implanted surface is softened by disordering and subsequent diffusion of Ta to A1 sites causes hardening of the surface.

Previously we reported a substantial (∼ 50 %) decrease in shear modulus prior to amorphization in Kr irradiated Zr3Al, and proposed that amorphization is triggered when the crystalline lattice becomes unstable against shear stress. In the present work, the relation between amorphization and shear elastic instability has been investigated in two additional compounds (FeTi and NiAl) during room temperature irradiation with 1.7-MeV Kr+. A shear modulus was measured using Brillouin scattering; structural information was obtained in situ in a high voltage electron microscope interfaced to a tandem accelerator.

During irradiation of FeTi, chemical disordering and a large (∼40 %) decrease of shear modulus were observed, and an amorphous phase developed subsequently. In contrast, NiAl remained crystalline and chemically ordered during irradiation, and exhibited only a ∼ 10 % decrease in shear modulus. Hence, these two results provide further support that a shear instability triggers irradiation-induced amorphization. The shear instability mechanism may also apply to other solid-state amorphization techniques, e.g. hydrogen charging and mechanical deformation.

NiTi was irradiated with Ni ions to study the rate of amorphization as a function of temperature and to determine the temperature cutoff for the crystalline-to-amorphous transition. A series of irradiations was conducted at different temperatures from ambient to 350 °C. Prior to irradiation, the specimens contained martensitic plates and austenitic (B2) regions. However, during irradiation at temperatures of 80 “C and higher, all the specimens were entirely austenitic. As expected, amorphization was delayed as the irradiation temperature was increased. The fraction of material that became amorphous after irradiation at 250 °C to a dose of 0.7 dpa was estimated to be 5 to 10%. Specimens irradiated at higher temperatures remained crystalline, even after doses as high as 4 dpa. Irrespective of the irradiation temperature, we found a non-uniform distribution of amorphous regions that exhibited a morphology closely resembling the shape of the martensitic plates that existed in the material prior to heating it to the irradiation temperature. These observations are discussed in terms of the influence of structural defects on the kinetics of amorphization.

The Ti-rich end of the Ti-(Co,Ni) was investigated by ion mixing. A metastable FCC phase was discovered which formed over a broad composition range. The stable phase was formed by ion mixing at 350°C in some samples but was not formed until 550°C during in situ heating in the Transmission electron microscope. Some of the Ni-rich ternary alloys did not amorphize even after liquid nitrogen ion irradiations. This result indicates that the amorphization mechanism for the TiNi CsCl phase is different from that of the TiCo CsCl phase.

Polycrystalline niobium was implanted with 200-keV C+ ions to a total fluence of 7 × 1017 carbon ions per cm2 (C/cm2). Auger electron spectroscopy (AES) analysis showed that the carbon concentration varied from 5 to 50 at.% within a depth of about 4000 Å. Glancing-angle x-ray diffraction analysis (XRDA) and transmission electron microscopy (TEM) analysis indicated that no Nb2C phase was formed and that a buried fee NbC layer was formed in the region where carbon content exceeds about 40 at.%. The absence of Nb2C was attributed to its narrow range of solubility for carbon and the low diffusivity of carbon atoms. The possibility of the NbC precipitation by nucleation and growth or by a diffusionless martensitic transformation is discussed. When the implanted samples were annealed at 1273 K for 1 h, an orthorhombic Nb2C phase formed as spherical precipitates and the implanted carbon redistributed.

The microstructuTe and mechanical properties of high purity aluminum implanted with 20 at.% oxygen to a depth of roughly 500 nm and subjected to various thermal histories have been examined. Transmission electron microscopy and Rutherford-backscattering spectrometry were used to characterize the depth and nature of the implanted zone. As implanted, the material appears to contain a homogeneous distribution of disordered precipitates with sizes of 1.5-3.5 nm. Annealing at 450 or 550ΰC for 1 hour, induces ordering of the precipitates but only causes slight coarsening. Ultra-low load indentation hardness testing was used to probe the mechanical response of the surface-modified material. The data from the hardness tests were interpreted through the use of a finite-element model; the results indicate the flow stresses of an implanted and annealed layer are as high as 1600 MPa. The as-implanted material is much harder, approaching 3300 MPa. The degree of strengthening expected for the as-implanted and post-annealed material on the basis of the observed microstructure was estimated using several micromechanical models, and the results conform to the findings from indentation testing.

The cencept of percolation can be applied to describe many phase transition problems(l) and various disordered systems(2). An infinite percolation cluster at percolation threshold (Pc) is one of the most prominent fractal system(3). The fractal structure of the percolation clusters makes it possible to connect the universal exponents in percolation transition and the geometrical scaling quantities, like fractal dimension Df. Increasing interest has recently been attractive to produce and study the ideal two-dimensional (2D) percolation films(4,5), which usually composed of a random mixture of crystalline and amorphous phases'(6). In this paper, we first report the direct observation of a percolation cluster consisting of two amorphous phases induced in thin solid films during crystalline-to-amorphous phase trnasformation by ion irradiation.

Focused Ar-ion laser and MeV ion beams were impinged onto stainless-steel foils to investigate the localized modification of the magnetic property associated with the phase transformation. The magnetic signal intensity of the Ar-ion laser irradiated areas was found to locally decrease at a laser power of 350 mW and almost extinguish at 550 mW with a beam spot size of 13.2 μm (at 1/e intensity) because of the localized retransformation into austenite. On the other hand, the magnetic signal intensity was found to increase by 3 MeV Au+ implantation because of the localized martensitic transformation. The magnetic signal for ferromagnetic substrates was much more enhanced than that for non-magnetic substrates. These results indicate that the beam-induced localized phase-transformation in stainless-steel can be applied to fixed magnetic recording.

Electron diffraction and imaging are used to characterize and contrast the structures and microstructures of a metastable Cr-Ti phase formed after quenching and a metastable Cu-Ti phase formed during electron irradiation. In both phases, marked structural anisotropies are found which have characteristics common to both of these bcc-based materials. It has been reported in the literature that this quenched-in metastable Cr-Ti phase undergoes a spontaneous structural relaxation into the amorphous state during sub-eutectoid temperature anneals [1]. Despite the similarity of the present experiments to those reported in the literature, an amorphization transformation was not observed. It is argued that the amorphization of this material requires the stabilization of the amorphous phase by an impurity.

Ion beam irradiation of Glassy Carbon is shown to increase its resistivity by up to eight orders of magnitude. These changes in resistivity are correlated with results obtained from Raman spectroscopy and Reflection High Energy Electron Diffraction. At high doses of C implantation there is convincing evidence that ion beam irradiation partially graphitizes the surface of Glassy Carbon.

The present contribution reports on measurements of the diffusion coefficients of Hf in a-Zr via the RBS technique. 250 8 Hf thin films were deposited on two kinds of polycrystalIine Zr samples and annealed in a 773-1115 K temperature range. Our results show that in both cases, the diffusion coefficients follow curved flrrhenius plots. On the other hand for the purest Zr sample we have obtained diffusion coefficients that are systematicaly and significativel ly lower than those corresponding to the Zr sample richer in impurities.

This paper presents the experimental observations of Fractal Aggregates on thin solid films after either directly thin film deposition or additional ion irradiation. A linear correlation was found between the fractal dimension and the atomic magneton of the aggregating particles of Fe, Co, Cr and Ni.

We studied the effect of varying the target temperature (by changing the beam power) on the structure and properties of nitrogen ion implanted 304 stainless steel. With a beam power of 0.1 W/ cm2 the target temperature is restricted to 150°C. After a dose of 3. 5x1017N2+/cm2 the microhardness measured at 10g increases by 15%. With a beam power of 1.1 W/cm2 the target temperature is 500°C. After the same dose as before, the irdcrohardness increase is 40%. Glancing Angle X-ray Diffraction and Auger depth profiling results suggest that the increased hardness is due to the presence of nitrogen in solution as opposed to complete precipitation. A sample deformed by compression formed an enhanced oxide layer during implantation. This oxide layer appears to have a capping action against the out-diffusion of nitrogen.

Ni-Ti films were bombarded by plasma source heavy ions of different ion dose and ion flux. Disc-like non-uniform microstructures were found when the films were irradiated at a dose of 5x1016Kr+/cm2. These “discs” were acting as defect centers. The development of “discs” depended on the plasma ion flux during the pulse. Target geometry appeared to have effects on the density of “discs”.

The effect of 1 MeV N+ irradiation on the microstructure of Fe and Ti specimens was investigated. The Fe and Ti specimens were implanted such that the N peak concentration (30 at.% in Fe, 45 at.% in Ti), was below the concentration of N in ε-Fe2N and δ-TiN, respectively. X-ray diffraction phase analysis showed that ε-Fe2N and δ-TiN had formed. X-ray diffraction stress analysis indicated that the residual stress in the Fe and Ti matrices was negligible after implantation. This suggests that the volume misfit due to nitride formation had been accommodated by plastic deformation. Indeed, surface profilometry of implanted Fe showed that a volume increase of the specimen had occurred which was compatible with the formation of unstrained nitride .

In using low temperature physical vapour deposition (PVD) techniques new metastable and amorphous materials can be deposited. Structural order in a coating is produced largely by the mobility of the adatoms. Low mobility does not allow the formation of equilibrium phases and metastable and/or amorphous structures are observed. These coatings have sufficient thermal stability for tools, and for both wear- and corrosion-protection. Examples are given within the systems Al-O-N, Ti-Al-N and Cr-Al-N and the properties, crystalline and thermodynamic state of the coatings are characterized. An example of decomposition phenomena is given in metastable thin coatings by the Ti-Zr-N system.