Jan Szmidt

Diamond-like carbon coatings for biomedical applications

Abstract The results of experimental studies on amorphous diamond carbon layers obtained by a new method of r.f. dense plasma chemical vapour deposition onto orthopaedic pins and screws are presented. Research on this subject which has been carried out over many years allows us to draw optimistic conclusions concerning the biomedical applications of diamond-like carbon (DLC). In particular, preliminary medical research on a new DLC-steel substrate system developed in 1992, which has just been concluded, is extremely promising.

Refractive index sensing of fiber optic long-period grating structures coated with a plasma deposited diamond-like carbon thin film

Long-period grating (LPG) structures including cascaded LPGs on step index fibers and photonic crystal fibers were coated with thin films of diamond-like carbon (DLC) using plasma deposition techniques. Improvements in the coating procedures increased sensitivity to external refractive index variations indicating significant improvements in sensing capability of the hybrid structures. DLC films in the range of tens of nanometers significantly increased sensitivity of all the structures tested.

Application of a composite plasmonic substrate for the suppression of an electromagnetic mode leakage in InGaN laser diodes

We demonstrate an InGaN laser diode, in which the waveguiding quality of the device is improved by the introduction of highly doped (plasmonic) layer constituting an upper part of the GaN substrate. Thanks to this, we were able to suppress the electromagnetic mode leakage into the substrate without generating additional strain in the structure, in contrast to the typical design relying on thick AlGaN claddings. The plasmonic substrate is built as a stack of gallium nitride layers of various electron concentrations deposited by a combination of hydride epitaxy and high-pressure solution method. The mentioned improvements led to the reduction of the threshold current density of our devices down to 2 kA/cm2 and to the optimization of the near and far field pattern.

Electrophysical properties of thin germanium/carbon layers produced on silicon using organometallic radio frequency plasma enhanced chemical vapor deposition process

Structural, chemical, optical and electronic properties of thin amorphous hydrogenated germanium/carbon films, produced from tetramethylgermanium by means of a radio frequency plasma enhanced chemical vapour deposition process, are described. The study reveals good quality of both the films themselves and the film/silicon interface. Strong dependence of chemical, optical and electronic properties on the RF power applied during deposition process makes the investigated materials promising candidates for applications in the field of multilayer optoelectronic systems. Substantial differences of refractive index (for the wavelength of 400 nm ranging from 1.68 to 3.35, depending on the RF power) suggest such a use as materials for interference multistate optical memories, for instance.

Application of diamond-like layers as gate dielectric in metal/insulator/semiconductor transistor

Abstract In this work the application of diamond-like carbon (DLC) layers formed by r.f. plasma-enhanced chemical vapour deposition (PECVD) as the dielectric layer in a metal/insulator/semiconductor (MIS) transistor (MISFET) is presented. In the course of this work the technology has been developed, enabling the manufacture of MIS transistors with DLC layers as gate insulator. The r.f. PECVD method was used for the formation of DLC layers. The transistors, with channel sizes ranging from 10 × 10 μm 2 to 200 × 200 μm 2 , were manufactured in a microelectronics standard technological laboratory. Selective etching of source and drain contact holes was performed by a “lift off” technique, which required some modifications to the typical MOSFET fabrication procedure. Auger electron spectroscopy measurements proved the high purity of the gate dielectric DLC films and the penetration of carbon into the silicon substrate. Both the measured electrical characteristics, transient and output, confirmed the transistor action of the manufactured MISFET.

Nanocrystalline C=N thin films

Abstract This paper discusses phase composition as well as electrical and optical properties of carbon-nitrogen (CN) compound obtained by reactive pulse plasma method. It is shown that material produced in such a way is a mixture of an amorphous compound which we have called polycyanoimine and nanocrystalline diamond. Its electrical and optical properties differ from those of DLC obtained by the same method. During electrical measurements there have not been observed diode-like current-voltage (I-V) characteristics, what rules out the possibility that nitrogen atoms might act as a dopant in obtained material. It has been found that electrical resistivity of investigated films, as ranging from 109 to 1011 Ωcm, has been higher than that of DLC layers produced from pulse plasma. However, subsequent low temperature (350 °C) annealing has resulted in the drop of their resistivity to the value of 106–107 Ωcm, the same as for DLC materials. Annealing has also influenced refractive index of investigated layers resulting in its increase from 1.9 to 2.13. Moreover, it has been observed that CN layers produced under the highest nitrogen pressure (i.e. 60 Pa) have been luminescent when illuminated with 514.5 nm laser beam, which does not occur in the case of DLC.

Step-edge-induced resistance anisotropy in quasi-free-standing bilayer chemical vapor deposition graphene on SiC

which results in macro steps � 10 nm in height. In this report, we study the qualitative and quantitative effects of SiC steps edges on the resistance of epitaxial graphene grown by chemical vapor deposition. We experimentally determine the value of step edge resistivity in hydrogen-intercalated QFS-bilayer graphene to be � 190Xlm for step height hS ¼ 10 nm and provide proof that it cannot originate from mechanical deformation of graphene but is likely to arise from lowered carrier concentration in the step area. Our results are confronted with the previously reported values of the step edge resistivity in monolayer graphene over SiC atomic steps. In our analysis, we focus on large-scale, statistical properties to foster the scalable technology of industrial graphene for electronics and sensor applications. V C 2014 AIP Publishing LLC .[ http://dx.doi.org/10.1063/1.4896581]

Electrical behaviour and breakdown in plasma deposited cubic BN layers

Abstract The paper presents results of an investigation of the electrical properties of cubic boron nitride (c-BN) layers deposited onto silicon substrates by the reactive pulse plasma method. Current-voltage characteristics of the layers in metal/insulator/semiconductor (MIS) structures were investigated in a wide voltage range for films of various thicknesses, obtained under different technological conditions. On the basis of I-V measurements, the breakdown properties of BN layers were also evaluated. In spite of many similarities of c-BN films to diamond-like carbon films, we have found a slightly different character of electrical properties. In most cases we observed switching phenomena and voltage-controlled negative resistance. The dielectric strength of investigated layers shows a wide range of critical electric fields in the range 0.5–6.0 MV cm −1 . An attempt to explain the observed effects on the basis of existing models, valid for similar materials, is also made.

Influence of annealing on reverse current of 4H-SiC Schottky diodes

Abstract In this work, we show results of our measurements of the forward and reverse I–V characteristics of Ni/4H-SiC Schottky rectifiers, which were observed prior and after annealing of devices in various gases (Ar, Ar+H2). We investigate the influence of temperature and atmosphere of annealing on diodes properties. The annealing has no influence on forward I–V characteristics, but the reverse leakage current is reduced as a result of decreasing number of surface states. This phenomenon decreases generation of minority carriers due to reduction of the number of available discrete energy levels in the bandgap of investigated material.

Comparison of the surface structure of carbon films deposited by different methods

Abstract Atomic force microscopy is used to estimate and compare surface morphology of the carbon coatings, prepared using radio frequency plasma chemical vapor deposition, pulsed cathodic are discharge, ion-beam deposition and hot-filament chemical vapor deposition. The difference in the surface structure was mentioned for each method of deposition. The influence of the surface morphology on the film properties is discussed.