Hugo Pattyn

Fretting wear of carbon-ion-implanted physical-vapour-deposited TiN coatings

Abstract Titanium carbonitride top-layers were prepared by selectively implanting 80 ke V C + ions into a physical-vapour-deposited TiN coating 2.8 μm thick. Rutherford-backscattering analysis showed that the implanted carbon depth distribution was the one predicted by the TRIM 87 calculation and that part of the implanted carbon had diffused out from the gaussian-like distribution towards the surface, where an ion-beam-assisted deposition of an ultrathin carbon overlayer had grown. For doses going from 2.8 × 10 16 to 7.8 × 10 16 ions cm -2 the effect of the carbon implantation on the fretting wear behaviour was investigated. Friction and wear measurements demonstrated a well-defined difference between as-plated TiN and carbon-implanted TiN. Related to the carbon implantation, it was observed that a low friction coefficient during break-in corresponds to a lower fretting wear damage.

Pulsed laser crystallization and doping for the fabrication of high-quality poly-Si TFTs

Abstract We review the various applications of pulsed lasers, working in the nanosecond regime, to prepare high-quality poly-Si TFTs. It is shown that the best device performances (field-effect mobilities in excess of 140 cm2/V·s) are achieved by pulsed excimer laser crystallization of unhydrogenated amorphous Si thin films. In addition, for source and drain formation, we demonstrate that the excimer laser induced diffusion of dopant from a solid source (spin-on phosphorus-doped silicate glass) is very attractive to achieve good electrical properties of the n-channel TFTs.

Nuclear orientation of on-line separated isotopes

Abstract On-line techniques have proven to be successful for the study of nuclei far from stability in performing spectroscopy. Further information on these short-lived nuclei can be obtained by measuring anisotopy coefficients of β- and γ-transitions. These measurements permit the clarifying of decay schemes and the study of nuclear moments. We thus propose the combination of on-line mass-separation with low temperature nuclear orientation. A system for this is being set up at the LISOL facility. The main part consists of a 3 He- 4 He dilution cryostat with high cooling power. It features a side-access port to allow direct implantation on the cold finger. A liquid helium cooled transport line with adjustable baffles makes the connection to the isotope separator. Nuclei with a lifetime down to a few minutes can be continuously implanted into a ferromagnetic host and oriented by the hyperfine field at temperatures lower than 30 mK. The limit of the lifetime is set by the spin-lattice relaxation time. In order to study shorter lived nuclei an “on-line” immediate orienting mechanism is installed: the beam line includes a UHV-chamber, where polarization is achieved by scattering at grazing incidence on a magnetized nickel single crystal. For preserving the obtained orientation during measurement the low temperature implantation is still required. Both mentioned orienting mechanisms completement each other for a nuclear study of short-lived isotopes. Sets of deflection plates and a movable part of the beam line allow a quick transition from one mode to another. Furthermore the cooled collecting foils can be changed in a short time without breaking the cooling cycle it removal of the daughter activities is requested.

Pulsed laser crystallization of hydrogen-free a-Si thin films for high-mobility poly-Si TFT fabrication

The possibility to fabricate high-mobility polysilicon TFTs by nanosecond pulsed laser crystallization of unhydrogenated amorphous Si thin films has been investigated. Two types of lasers have been used: a large area (≈ 1 cm2) single ArF excimer laser pulse and a small diameter (≈ 100 μm) frequency-doubled Nd:YAG laser beam, working in the scanning regime. Processed films have been characterized in detail by different optical and microscopic techniques. Device performances indicate that the best results are achieved with the excimer laser leading to high mobility values (up to 140 cm2/Vs) which are much larger than in polysilicon TFTs fabricated onto the same quartz substrates by low-temperature thermal (630° C) crystallization of amorphous Si films (μfe≈55 cm2/Vs).

Importance of channeled implantation to the synthesis of erbium silicide layers

166Er atoms were implanted with an energy of 70 to 90 keV and doses of 0.8 to 2.0×1017/cm2 into Si(111) substrates at temperatures ranging from 450 to 530 °C. We found that using conventional nonchanneled implantation at energies of ∼90 keV, it is impossible to form a continuous ErSi1.7 layer. At best, after annealing, a discontinuous ErSi1.7 layer with poor crystalline quality (χmin=40%) is obtained. On the contrary, using channeled implantation, a continuous epitaxial ErSi1.7 layer with very good crystalline quality can be formed; a lowest χmin value of 1.5% for a surface ErSi1.7 layer has been obtained. The origin of this different behavior is explained. Our results show that for synthesizing continuous ErSi1.7 layers with good quality using ion beam synthesis at energies around 90 keV, channeled implantation is indispensable.

Formation of buried and surface cosi2 layers by ion-implantation

Abstract The formation is studied of buried CoSi 2 layers and surface CoSi 2 layers formed by high-dose ion implantation in an energy range of 30 to 160 keV combined with conventional furnace annealing or with rapid thermal processing. The crystalline quality, the phase of the buried and surface silicide layers, the abruptness of the interfaces and the electrical transport properties are studied by RBS, channeling, cross-sectional TEM, Mossbauer spectroscopy and resistivity measurements. The stability of the buried and surface CoSi 2 layers at temperatures between 1000°C and 1200°C is also studied and compared with the results for MBE-grown samples.

Ti–B and Ti–B–C coatings deposited by plasma immersion ion implantation and their fretting behavior

Abstract Ti–B and Ti–B–C coatings were deposited by a two-step plasma immersion ion implantation (PIII) process. A structural study revealed that as-deposited PIII Ti–B coatings are amorphous and did not crystallize on vacuum annealing up to 800 °C. The coefficient of friction and the wear rate of such as-deposited and annealed PIII Ti–B coatings sliding against corundum under non-lubricated conditions were found to be higher than the ones for crystalline TiB 2 coatings deposited by PVD. Attempts to decrease friction and wear rate resulted in depositing PIII Ti–B based coatings in a methane atmosphere. Such PIII Ti–B–C coatings contain both hard TiB 2 and lubricating DLC phases. They show in non-lubricated fretting test conditions, a low coefficient of friction and a good wear resistance in comparison to industrial currently available PVD TiB 2 and PVD TiN coatings.

COMPREHENSIVE RUTHERFORD BACKSCATTERING AND CHANNELING STUDY OF ION-BEAM-SYNTHESIZED ERSI1.7 LAYERS

Heteroepitaxial ErSi1.7 layers with excellent crystallinity (χmin of Er is 1.5%) have been prepared by high‐dose 90 keV Er implantation into a Si(111) substrate using channeled implantation. Such an ErSi1.7/Si system offers a rare opportunity to study comprehensively the structure, orientation, and strain using Rutherford backscattering spectrometry and channeling analysis. We found that the minimum yield and width of the [0001] dip of the Er atoms are quite different from that of the Si atoms in the silicide layer. It is confirmed that the azimuthal orientation of the hexagonal ErSi1.7 layer to the cubic Si substrate is ErSi1.7 [0001] ∥ Si[111] and ErSi1.7 {1120} ∥ Si {110}, and that the epilayer is compressively strained. Besides, by using the angular scan and image scan, we reveal that the dips of the {1010} family are missing for the Si atoms in the epilayer but do exist for the Er atoms in the same epilayer. The reason for this drastic difference is explained by the separate {1010} planes and the ...

LISOL, the Leuven isotope separator on-line at the “cyclone”-cyclotron

Abstract LISOL, a mass separator with associated spectroscopy equipment has been brought into on-line operation at the isochronous cyclotron in Louvain-la-Neuve, Belgium. The facility enables studies of short-lived neutron-deficient isotopes. They are produced by nuclear projectiles with mass numbers up to 20 impinging on targets which are integrated into the separator ion source. Examples are given for α-induced reactions in a liquid-tin target and for 14 N-induced reactions in heated Mo-targets. Mass-separated reaction products can be guided to either one of three experimental terminals for on-line investigation. A moving-tape transport system can bring an accumulated radioactivity to detectors or spectrometers for γ-rays, conversion electrons, β-rays or charged particles. A multi-mass collector can accumulate simultaneously radio-activities from other mass chains for semi on-line detection. Nuclei as neutron deficient as 104 In and 103 In have already been investigated.

Carbonaceous surface layers deposited on TiN coatings by ion implantation

TiN coatings deposited by physical vapor deposition have been subjected to a postdeposition treatment involving beam line implantation with 80‐keV C+ ions at doses between 1×1017 and 3×1017 ions/cm2. Rutherford backscattering spectrometry measurements showed Gaussian‐like implantation‐depth profiles extending towards the surface which was found to be covered with carbon. The carbonaceous surface layer was characterized by Raman spectroscopy revealing the typical band features of diamondlike carbon. Simulations of the carbon depth profile indicate that the opaque carbon layer was formed from carbon in excess of the implanted dose. Further experiments suggest that the carbon layer resulted from an ion‐beam‐assisted deposition process. Fretting wear tests demonstrated lower friction and improved wear resistance of the TiN covered with the diamondlike carbon layer in comparison with as‐deposited TiN.