Texture in thin film silicides and germanides : a review

Silicides and germanides are compounds consisting of a metal and silicon or germanium. In the microelectronics industry, silicides are the material of choice for contacting silicon based devices (over the years, CoSi2, C54-TiSi2, and NiSi have been adopted), while germanides are considered as a top candidate for contacting future germanium based electronics. Since also strain engineering through the use of Si1-xGex in the source/drain/gate regions of MOSFET devices is an important technique for improving device characteristics in modern Si-based microelectronics industry, a profound understanding of the formation of silicide/germanide contacts to silicon and germanium is of utmost importance. The crystallographic texture of these films, which is defined as the statistical distribution of the orientation of the grains in the film, has been the subject of scientific studies since the 1970s. Different types of texture like epitaxy, axiotaxy, fiber, or combinations thereof have been observed in such films. In recent years, it has become increasingly clear that film texture can have a profound influence on the formation and stability of silicide/germanide contacts, as it controls the type and orientation of grain boundaries (affecting diffusion and agglomeration) and the interface energy (affecting nucleation during the solid-state reaction). Furthermore, the texture also has an impact on the electrical characteristics of the contact, as the orientation and size of individual grains influences functional properties such as contact resistance and sheet resistance and will induce local variations in strain and Schottky barrier height. This review aims to give a comprehensive overview of the scientific work that has been published in the field of texture studies on thin film silicide/germanide contacts. Published by AIP Publishing

Optimization of the annealing conditions for thin VO2 ALD films

Vanadium dioxide (VO2) is an intriguing material due to its semiconductor-metal transition (SMT). During this transition, which occurs near 67°C, electrical as well as optical properties change drastically. Possible applications include thermochromic windows, and memories or switches in micro- and optoelectronics. Although atomic layer deposition (ALD) is gaining importance for some of these applications, the growth of VO2 with this technique is not obvious, since in most cases V2O5 is obtained. In our previous work we presented ALD growth of VO2 by using Tetrakis[EthylMethylAmino]Vanadium and ozone at a temperature of 150°C [1]. XPS revealed the 4+ oxidation state of vanadium, indicating growth of VO2. Post-ALD thermal processing proved essential to crystallize the VO2 in the desired tetragonal phase (R). In this work we present the influence of the oxygen partial pressure on phase formation during such thermal processes. Additionally the influence of film thickness and annealing temperature on the post-annealing properties were studied, including morphology and SMT characteristics. During thermal processing a minimum oxygen partial pressure of approximately 1 Pa is indispensable to form crystalline VO2 (R) (figure 1). Oxygen partial pressures above 2 Pa show an intermediate monoclinic phase (B), which transforms to VO2 (R) at higher temperatures. At a value of 35 Pa this VO2 (B) phase finally transforms to V6O13 instead of VO2 (R). For very thin films, the thermal post-processing may result in agglomeration of the VO2 layers on the SiO2 substrate. Samples with a film thickness above 20nm show a typical resistivity ratio during the SMT of more than 2 orders of magnitude when annealed in the range 450°C to 500°C. For thinner films or higher annealing temperatures the resistivity ratio is suppressed and an overall increased resistivity is observed due to agglomeration (figure 2)

Ageing playfully: advancing research on games for older adults beyond accessibility and health benefits

Games for older adults have previously been explored with a focus on improving older adults’ well-being by fostering social interaction, and providing cognitive and physical stimulation, suggesting that they are a means of encouraging older adults to better themselves and introducing an overly functionalist perspective on play. In this workshop, we aim to shift perspectives on games for older adults on hedonic aspects that extend beyond benefits they provide. We will explore challenges and opportunities in the design and development of games for older adults that primarily focus on entertainment to create empowering and engaging experiences, and we will explore how to consolidate efforts that aim to deliver benefits of games with a purpose beyond entertainment to older adults

Semiconductor-metal transition in thin VO2 films grown by ozone based atomic layer deposition

Vanadium dioxide (VO2) has the interesting feature that it undergoes a reversible semiconductor-metal transition (SMT) when the temperature is varied near its transition temperature at 68°C.1 The variation in optical constants makes VO2 useful as a coating material for e.g. thermochromic windows,2 while the associated change in resistivity could be interesting for applications in microelectronics, e.g. for resistive switches and memories.3 Due to aggressive scaling and increasing integration complexity, atomic layer deposition (ALD) is gaining importance for depositing oxides in microelectronics. However, attempts to deposit VO2 by ALD result in most cases in the undesirable V2O5. In the present work, we demonstrate the growth of VO2 by using Tetrakis[EthylMethylAmino]Vanadium and ozone in an ALD process at only 150°C. XPS reveals a 4+ oxidation state for the vanadium, related to VO2. Films deposited on SiO2 are amorphous, but during a thermal treatment in inert gas at 450°C VO2(R) is formed as the first and only crystalline phase. The semiconductor-metal transition has been observed both with in-situ X-ray diffraction and resistivity measurements. Near a temperature of 67°C, the crystal structure changes from VO2(M1) below the transition temperature to VO2(R) above with a hysteresis of 12°C. Correlated to this phase change, the resistivity varies over more than 2 orders of magnitude

Formation of ultrathin Ni germanides : solid-phase reaction, morphology and texture

The solid-phase reaction of ultrathin (<= 10 nm) Ni films with different Ge substrates (single-crystalline (100), polycrystalline, and amorphous) was studied. As thickness goes down, thin film texture becomes a dominant factor in both the film's phase formation and morphological evolution. As a consequence, certain metastable microstructures are epitaxially stabilized on crystalline substrates, such as the epsilon-Ni5Ge3 phase or a strained NiGe crystal structure on the single-crystalline substrates. Similarly, the destabilizing effect of axiotaxial texture on the film's morphology becomes more pronounced as film thicknesses become smaller. These effects are contrasted by the evolution of germanide films on amorphous substrates, on which neither epitaxy nor axiotaxy can form, i.e. none of the (de) stabilizing effects of texture are observed. The crystallization of such amorphous substrates however, drives the film breakup

Recommendations for the Use of Serious Games in Neurodegenerative Disorders: 2016 Delphi Panel

International audienceThe use of Serious Games (SG) in the health domain is expanding. In the field of neurodegenerative disorders (ND) such as Alzheimer’s disease, SG are currently employed both to support and improve the assessment of different functional and cognitive abilities, and to provide alternative solutions for patients’ treatment, stimulation, and rehabilitation. As the field is quite young, recommendations on the use of SG in people with ND are still rare. In 2014 we proposed some initial recommendations (Robert et al., 2014). The aim of the present work was to update them, thanks to opinions gathered by experts in the field during an expert Delphi panel. Results confirmed that SG are adapted to elderly people with mild cognitive impairment (MCI) and dementia, and can be employed for several purposes, including assessment, stimulation, and improving wellbeing, with some differences depending on the population (e.g., physical stimulation may be better suited for people with MCI). SG are more adapted for use with trained caregivers (both at home and in clinical settings), with a frequency ranging from 2 to 4 times a week. Importantly, the target of SG, their frequency of use and the context in which they are played depend on the SG typology (e.g., Exergame, cognitive game), and should be personalized with the help of a clinician

Recommendations for the Use of Serious Games in Neurodegenerative Disorders: 2016 Delphi Panel

The use of Serious Games (SG) in the health domain is expanding. In the field of neurodegenerative disorders (ND) such as Alzheimer’s disease, SG are currently employed both to support and improve the assessment of different functional and cognitive abilities, and to provide alternative solutions for patients’ treatment, stimulation, and rehabilitation. As the field is quite young, recommendations on the use of SG in people with ND are still rare. In 2014 we proposed some initial recommendations (Robert et al., 2014). The aim of the present work was to update them, thanks to opinions gathered by experts in the field during an expert Delphi panel. Results confirmed that SG are adapted to elderly people with mild cognitive impairment (MCI) and dementia, and can be employed for several purposes, including assessment, stimulation, and improving wellbeing, with some differences depending on the population (e.g., physical stimulation may be better suited for people with MCI). SG are more adapted for use with trained caregivers (both at home and in clinical settings), with a frequency ranging from 2 to 4 times a week. Importantly, the target of SG, their frequency of use and the context in which they are played depend on the SG typology (e.g., Exergame, cognitive game), and should be personalized with the help of a clinician

A qualitative inquiry into the meaning of digital games for an older audience in Flanders

status: publishe