The formation and growth of hydrogen bubbles on a Si(1 0 0) surface during its anisotropic etching in aqueous KOH has been investigated. Quantitative data on bubble size, lifetime and density on the etching surface was obtained and their dependence on KOH concentration, applied potential and temperature were measured. In situ FTIR measurements demonstrated a strong dependence of bubble attachment on surface termination and hence on the hydrophilicity of the Si(1 0 0) surface during etching. The formation of surface defects and the geometry of bubble imprints have been directly characterised with scanning probe microscopy. The analysis of hillock formation and statistical considerations show that the adhesion of hydrogen bubbles during anisotropic etching of silicon is a source of surface roughness and pyramid formation.

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Time domain impedance spectroscopy (TDIS), potential step experiments, and in-situ infrared spectroscopy (FTIR) have been used to probe the surface termination of silicon (100) in contact with aqueous potassium hydroxide. TDIS allowed time-dependent measurements of the space charge capacitance with a time resolution of ∼100 μs and was used to probe the interfacial potential and charge distribution. From this, an analysis of the surface termination could be made. For p-Si(100) these measurements suggest that the hydrogen termination present at negative potentials is replaced by polar Si−O−Si bridges between neighboring surface silicon atoms at anodic peak potentials. The changes in surface termination have a time constant of ∼1 s, which is slow compared with the time resolution of TDIS. Time-resolved Mott−Schottky plots could be constructed for both p- and n-Si(100). A flat band potential of −0.55 V was obtained for p-Si(100). For n-Si(100), the technique allowed space charge capacitance measurements that were sufficiently short to obviate surface passivation. Therefore, space charge capacitance measurements could be extended far into the passive potential range, from which a flat band potential of −0.85 V vs SCE was obtained.

Introduction There are no evidence-based recommendations for the post-operative treatment and application of soft or rigid cervical collars after operative treatment of injuries of the subaxial cervical spine. Cervical collars can restrict peak range of motion and serve as a reminder to the patient. However, they can also cause pressure ulcers. The aim of this online-based survey among German spine centres was to gain an overview of post-operative treatment and the application of soft or rigid cervical collars after surgical treatment of injuries of the subaxial cervical spine. Materials and Methods An online-based survey was conducted among 59 spine centres certified by the German Spine Society. It comprised seven items and the option of adding remarks in the form of open-ended responses. Results The return rate was 63% (37 out of 59). Of the 37 analysed spine centres, 51% routinely apply a cervical collar post-operatively, 27% apply a soft and 16% a rigid cervical collar, 8% sequentially apply first a rigid and later a soft cervical collar. Less than half of the spine centres (43%) routinely use no cervical collar. Rigid collars are applied for more than 6 weeks and soft collars up to 6 weeks at some spine centres. Standardised post-operative treatment plans are common. The selection of the post-operative treatment plan depends primarily on the type of injury and method of operation and partly on patient age and bone quality. The satisfaction of German spine centres with the current handling of post-operative treatment of subaxial cervical spine injuries is high. Discussion The post-operative treatment of injuries of the subaxial cervical spine at German spine centres is heterogeneous, and the evidence on advantages and disadvantages of the post-operative application of cervical collars is insufficient. Planning and implementation of randomised controlled clinical trials in subaxial cervical spine injuries is challenging.