Selective epitaxial growth in silicon on insulator: Planarity and mass flow

Seeded zone-melt recrystallization using a dual electron beam system has been performed on silicon-on-insulator material, which was prepared with single-crystal silicon filling of the seed windows by selective epitaxial growth. The crystal quality has been assessed by a variety of microscopic techniques, and it is shown that single-crystal films 0.5-1.0 μm thick over 1.0 μm of isolating oxide may be prepared by this method. These films have considerably less lateral variation in thickness than standard material, in which the windows are not so filled. The filling method is suitable for both single- and multiple-layer silicon-on-insulator, and gives the advantages of excellent layer uniformity after recrystallization and improved planarity of the whole chip structure. Experiments using various amounts of seed window filling have shown that the lateral variations of silicon film thickness seen in unplanarized material are due to stress relief in the cap oxide when the silicon film is molten, rather than the effect previously postulated in which they were assumed to be due to the contraction of silicon on melting.

Performance of CMOS Devices in Silicon-on-Sapphire Films After Solid-Phase Epitaxial Growth With Rapid Electron-Beam Heating

The crystal quality of 0.3-μm-thick as-grown epitaxial silicon-on-sapphire (SOS) was improved using solid-phase epitaxy (SPE) by implantation with silicon to 1015 ions/cm2 at 175 keV and rapid annealing using electron-beam heating, n-channel and p-channel transistormobilities increased by 31 and 19 percent, respectively, and a reduction in ring-oscillator stage delay confirmed that crystal defects near the upper silicon surface had been removed. Leakage in n-channel transistors was not significantly affected by the regrowth process but for p-channel transistors back-channel leakage was considerably greater than for the control devices. This is attributed to aluminum released by damage to the sapphire during silicon implantation. © 1985 IEEE

Development of a universal stress sensor for graphene and carbon fibres

Carbon fibres are a significant volume fraction of modern structural airframes. Embedded into polymer matrices, they provide significant strength and stiffness gains by unit weight compared with competing structural materials. Here we use the Raman G peak to assess the response of carbon fibres to the application of strain, with reference to the response of graphene itself. Our data highlight the predominance of the in-plane graphene properties in all graphitic structures examined. A universal master plot relating the G peak strain sensitivity to tensile modulus of all types of carbon fibres, as well as graphene, is presented. We derive a universal value of - average - phonon shift rate with axial stress of around -5ω0 -1 (cm -1 Mpa-1), where ω0 is the G peak position at zero stress for both graphene and carbon fibre with annular morphology. The use of this for stress measurements in a variety of applications is discussed. © 2011 Macmillan Publishers Limited. All rights reserved.

Strong plasmonic enhancement of photovoltage in graphene

From the wide spectrum of potential applications of graphene, ranging from transistors and chemical sensors to nanoelectromechanical devices and composites, the field of photonics and optoelectronics is believed to be one of the most promising. Indeed, graphene's suitability for high-speed photodetection was demonstrated in an optical communication link operating at 10 Gbit s 1. However, the low responsivity of graphene-based photodetectors compared with traditional III-V-based ones is a potential drawback. Here we show that, by combining graphene with plasmonic nanostructures, the efficiency of graphene-based photodetectors can be increased by up to 20 times, because of efficient field concentration in the area of a p-n junction. Additionally, wavelength and polarization selectivity can be achieved by employing nanostructures of different geometries. © 2011 Macmillan Publishers Limited. All rights reserved.

Ultrafast and high-energy pulsed lasers with graphene mode-lockers

The conventional technology for generating ultrashort pulses relies on soliton-like operation based mode-locking. In this regime, the pulse duration is limited by nonlinear optical effects[1]. One method to mitigate these effects is to alternate segments of normal and anomalous group velocity dispersion (GVD) fiber[1]. This configuration is known as dispersion-managed soliton design. It decreases the nonlinear optical effects and reduces the pulse duration[1]. © 2011 IEEE.

Non-linear photoluminescence from graphene

Graphene is in the focus of research due to its unique electronic and optical properties. Intrinsic graphene is a zero gap semiconductor with a linear dispersion relation for E-k leading to zero-effective-mass electrons and holes described by Fermi-Dirac theory. Since pristine graphene has no bandgap no photoluminescence would be expected. However, recently several groups showed non-linear photoluminescence from pristine graphene putting forward different physical models explaining this remarkable effect [1-3]. © 2011 IEEE.

Wideband tunable, high-power, graphene mode-locked ultrafast lasers

Ultrafast passively mode-locked lasers with spectral tuning capability and high output power have widespread applications in biomedical research, spectroscopy and telecommunications [1,2]. Currently, the dominant technology is based on semiconductor saturable absorber mirrors (SESAMs) [2,3]. However, these typically have a narrow tuning range, and require complex fabrication and packaging [2,3]. A simple, cost-effective alternative is to use Single Wall Carbon Nanotubes (SWNTs) [4,10] and Graphene [10,14]. Wide-band operation is possible using SWNTs with a wide diameter distribution [5,10]. However, SWNTs not in resonance are not used and may contribute to unwanted insertion losses [10]. The linear dispersion of the Dirac electrons in graphene offers an ideal solution for wideband ultrafast pulse generation [10,15]. © 2011 IEEE.