Recent developments in vertical MOSFETs and SiGe HBTs, Journal of Telecommunications and Information Technology, 2004, nr 1

There is a well recognised need to introduce new materials and device architectures to Si technology to achieve the objectives set by the international roadmap. This paper summarises our work in two areas: vertical MOSFETs, which can allow increased current drive per unit area of Si chip and SiGe HBT's in silicon-on-insulator technology, which bring together and promise to extend the very high frequency performance of SiGe HBT's with SOI-CMOS

Review and perspective of high-k dielectrics on silicon, Journal of Telecommunications and Information Technology, 2007, nr 2

The paper reviews recent work in the area of high-k dielectrics for application as the gate oxide in advanced MOSFETs. Following a review of relevant dielectric physics, we discuss challenges and issues relating to characterization of the dielectrics, which are compounded by electron trapping phenomena in the microsecond regime. Nearly all practical methods of preparation result in a thin interfacial layer generally of the form SiOx or a mixed oxide between Si and the high-k so that the extraction of the dielectric constant is complicated and values must be qualified by error analysis. The discussion is initially focussed on HfO2 but recognizing the propensity for crystallization of that material at modest temperatures, we discuss and review also, hafnia silicates and aluminates which have the potential for integration into a full CMOS process. The paper is concluded with a perspective on material contenders for the “end of road map” at the 22 nm node

TiO₂–Graphene Oxide and TiO₂–Reduced Graphene Oxide Composite Thin Films for Solar Photocatalytic Wastewater Treatment

This research reports on Vis- and solar-active photocatalytic bi-layered films of TiO2 (layer 1) and a composite with TiO2 matrix and graphene oxide or reduced graphene oxide filler (layer 2) obtained by coupling two methods: spray pyrolysis deposition followed by spraying a diluted sol. The thin films crystallinity degree, surface morphology and elemental composition were recorded and the composites were tested in photo-degradation processes, using the standard 10 ppm methylene blue solution, under simulated UV + VIS irradiation conditions using an irradiance measured to be close to the natural one, in continuous flow process, at demonstrator scale; these results were compared with those recorded when using low irradiance values in static regime. The effect of the increase in the graphene oxide content was investigated in the concentration range 1.4%w...10%w and was found to increase the process efficiency. However, the photocatalytic efficiencies increased only by 15% at high irradiance values compared with the values recorded at low irradiance as result of the electron-hole recombination in the composite-thin film. Similar experiments were run using composites having reduced graphene oxide as filler. The interfaces developed between the matrix and the filler were discussed outlining the influence of the filler’s polarity. The thin films stability in aqueous medium was good, confirmed by the results that outlined no significant differences in the surface aspect after three successive photocatalytic cycles

RF Magnetron Sputtering Deposition of TiO2 Thin Films in a Small Continuous Oxygen Flow Rate

Rutile titanium oxide (TiO2) thin films require more energy to crystallize than the anatase phase of TiO2. It is a prime candidate for micro-optoelectronics and is usually obtained either by high substrate temperature, applying a substrate bias, pulsed gas flow to modify the pressure, or ex situ annealing. In the present work, we managed to obtain high enough energy at the substrate in order for the particles to form rutile TiO2 at room temperature without any intentional substrate bias in a continuous gas flow. The rutile TiO2 thin films were deposited by a reactive radiofrequency magnetron sputtering system from a titanium target, in an argon/oxygen gas mixture. Investigations regarding the film’s structure and morphology were performed by X-ray diffraction (XRD), X-ray reflectivity (XRR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX), while the optical properties were investigated by means of ellipsometry

Recent developments in vertical MOSFETs and SiGe HBTs

There is a well recognised need to introduce new materials and device architectures to Si technology to achieve the objectives set by the international roadmap. This paper summarises our work in two areas: vertical MOSFETs, which can allow increased current drive per unit area of Si chip and SiGe HBTs in silicon on insulator technology, which bring together and promise to extend the very high frequency performance of SiGe HBTs with SOI-CMO

Nanocrystalline graphite thin layers for low-strain, high-sensitivity piezoresistive sensing

Bulk nanocrystalline graphite has been investigated as a possible candidate for piezoresistive sensors. The thin films were grown using capacitively coupled plasma enhanced chemical vapor deposition and a technological workflow for the transfer of the active material onto flexible substrates was established in order to use the material as a piezoresitive element. Preliminary electrical measurements under mechanical strain were performed in order to test the piezoresistive response of the material and promising GF values of 50 − 250 at 1% strain were obtained

Evolution of Nanocrystalline Graphite’s Physical Properties during Film Formation

Nanocrystalline graphite (NCG) layers represent a good alternative to graphene for the development of various applications, using large area, complementary metal-oxide semiconductor (CMOS) compatible technologies. A comprehensive analysis of the physical properties of NCG layers—grown for different time periods via plasma-enhanced chemical vapour deposition (PECVD)—was conducted. The correlation between measured properties (thickness, optical constants, Raman response, electrical performance, and surface morphology) and growth time was established to further develop various functional structures. All thin films show an increased grain size and improved crystalline structure, with better electrical properties, as the plasma growth time is increased. Moreover, the spectroscopic ellipsometry investigations of their thickness and optical constants, together with the surface roughness extracted from the atomic force microscopy examinations and the electrical properties resulting from Hall measurements, point out the transition from nucleation to three-dimensional growth in the PECVD process around the five-minute mark