Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

We have studied intrinsic and impurity related defects in silicon carbide (SiC) epilayers grown with fast epitaxy using chemical vapor deposition in a vertical hot-wall reactor. Using capacitance transient techniques, we have detected low concentrations of electron traps (denoted as Z1/2, EH6/7 and titanium) and hole traps (denoted as HS1 and shallow boron) in the n-type 4H–SiC epilayers. The concentration of intrinsic defects (Z1/2, EH6/7, and HS1 centers) increases with increasing growth temperature. The incorporation of shallow boron (B) decreases at higher growth temperatures, whereas the titanium (Ti) concentration is not sensitive to the growth temperature. The concentration of shallow B and Ti increases with increasing C/Si ratio. The concentration of the EH6/7 and the HS1 centers however, decreases with increasing C/Si ratio. We have also tested graphite susceptors with TaC or SiC coating and observed that the purity of the susceptor material plays a critical role in reducing the background impurity incorporation. The correlation with the carrier lifetime of these epilayers indicates that the EH6/7 and the Z1/2 centers may be the lifetime limiting defects in the investigated epilayers.

Electrically active defects in n-type 4H-silicon carbide grown in a vertical hot-wall reactor

Silicon carbide (SiC) has been around for more than 100 years as an industrial material and has found wide and varied applications because of its unique electrical and thermal properties. In recent years there has been increased attention to SiC as a viable material for biomedical applications. Of particular interest in this review is its potential for application as a biotransducer in biosensors. Among these applications are those where SiC is used as a substrate material, taking advantage of its surface chemical, tribological and electrical properties. In addition, its potential for integration as system on a chip and those applications where SiC is used as an active material make it a suitable substrate for micro-device fabrication. This review highlights the critical properties of SiC for application as a biosensor and reviews recent work reported on using SiC as an active or passive material in biotransducers and biosensors.

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Silicon carbide: a versatile material for biosensor applications

Bulk and epitaxial growth of silicon carbide

The growth of thick epitaxial SiC layers needed for high-voltage, high-power devices is described for two types (horizontal and vertical) of hot-wall (HW) CVD reactors. In both cases, the advantages of HWCVD are the better cracking efficiency of the precursor gases and better temperature distribution together with low input power. Characterizations of some examples of thick SiC layers grown are given.

Thick Silicon Carbide Homoepitaxial Layers Grown by CVD Techniques

Two high temperature CVD techniques, respectively optimised for epitaxial and crystal growth, are presented. A chimney reactor has been developed for fast epitaxy, carried out at 1700‐1900°C, with growth rates ranging from 10 to 25 m mh 1 , and a material quality close to conventional CVD processes. The growth of 4H-SiC epilayers with low n-type doping (10 14 ‐10 15 cm 3 ) and carrier lifetimes up to 0.4 ms is described, while the feasibility of high voltage Schottky rectifiers (1.8 kV) is demonstrated. On the other side, developments of the stagnant flow HTCVD process, where growth is carried out at 2000‐2300°C, are shown to enable growth rates ranging from 0.3 up to 0.8 mm h 1 . The main characteristics of HTCVD grown SiC crystals (up to nearly 7 mm thick) are described. © 1999 Elsevier Science S.A. All rights reserved.

A. Vorob’ev

Papers

High temperature CVD growth of SiC