Extending the resolution and spatial proximity of lithographic patterning below critical dimensions of 20 nm remains a key challenge with very-large-scale integration, especially if the persistent scaling of silicon electronic devices is sustained. One approach, which relies upon the directed self-assembly of block copolymers by chemical-epitaxy, is capable of achieving high density 1 : 1 patterning with critical dimensions approaching 5 nm. Herein, we outline an integration-favourable strategy for fabricating high areal density arrays of aligned silicon nanowires by directed self-assembly of a PS-b-PMMA block copolymer nanopatterns with a L(0) (pitch) of 42 nm, on chemically pre-patterned surfaces. Parallel arrays (5 × 10(6) wires per cm) of uni-directional and isolated silicon nanowires on insulator substrates with critical dimension ranging from 15 to 19 nm were fabricated by using precision plasma etch processes; with each stage monitored by electron microscopy. This step-by-step approach provides detailed information on interfacial oxide formation at the device silicon layer, the polystyrene profile during plasma etching, final critical dimension uniformity and line edge roughness variation nanowire during processing. The resulting silicon-nanowire array devices exhibit Schottky-type behaviour and a clear field-effect. The measured values for resistivity and specific contact resistance were ((2.6 ± 1.2) × 10(5)Ωcm) and ((240 ± 80) Ωcm(2)) respectively. These values are typical for intrinsic (un-doped) silicon when contacted by high work function metal albeit counterintuitive as the resistivity of the starting wafer (∼10 Ωcm) is 4 orders of magnitude lower. In essence, the nanowires are so small and consist of so few atoms, that statistically, at the original doping level each nanowire contains less than a single dopant atom and consequently exhibits the electrical behaviour of the un-doped host material. Moreover this indicates that the processing successfully avoided unintentional doping. Therefore our approach permits tuning of the device steps to contact the nanowires functionality through careful selection of the initial bulk starting material and/or by means of post processing steps e.g. thermal annealing of metal contacts to produce high performance devices. We envision that such a controllable process, combined with the precision patterning of the aligned block copolymer nanopatterns, could prolong the scaling of nanoelectronics and potentially enable the fabrication of dense, parallel arrays of multi-gate field effect transistors.
Resistance contributions in a nanowire device are determined accurately. Resistance in silver nanowires, such as conduction‐channel and contact resistance, including current‐crowding effects, reveal both the true nanowire resistivity and the overall device performance, including dissipation and scaling potential. A comprehensive study on the device layout, the contact geometry and, most importantly, the transfer length over which charge injection between contact electrode and nanowire occurs, is performed.
The reaction of molecular oxygen with the Si(111)-7 x 7 surface is investigated at room temperature using in situ scanning tunneling microscopy and surface stress measurements to reveal the quantitative relationship between site-specific oxygen coverage and a decrease in tensile surface stress. This relationship is described using a modified form of the reaction model originally proposed by Dujardin et al. We show that the decrease in tensile surface stress is greatest for the faulted subunits of the 7 x 7 cell and determine the stress signatures of different reaction products, including the absence of long-lived metastable species with a unique stress signature.
The current in vitro diagnostic design process is a combination of methods from engineering disciplines and from government regulatory agencies. The goal of design processes that have been developed is to ensure that a new product meets the user’s expectations and is safe and effective in providing its claimed benefits and proper functioning, otherwise known as the essential design outputs. In order to improve the ability of designers and auditors to ascertain the safety and efficacy of a product, the use of design controls has been adopted that specify a method of evaluating the design process at several key stages. The main objective of this research was to examine the resolution and architectural details necessary to build an adequate manufacturing control system to assure the EDO outputs in large IVD instruments in the company under study. The control system is the defined inspections and test processes to delineate between acceptable and unacceptable product before release for sale. The authors reviewed current design control regulatory requirements within the IVD industry, as well as design controls in other regulated industries. This research was completed to determine what opportunities could be transferred to large in-vitro IVD instruments using an IVD manufacturer as a case study. In conclusion, the research identified three areas where a properly configured EDO can add value within IVD instrument design and manufacture, namely: (1) development of a control system which is fit for purpose; (2) a mechanism to manage and proliferate key design knowledge within the organisation and thereby manage outsourced services; and (3) implementing a scaled engineering change process because changes impacting EDO naturally require extra regulatory and engineering oversight.
We describe a simple method to heat a free-standing sample such as a cantilever using bimetallic strips. The bimetallic strips are used to make controlled electrical contacts induced by radiative heating of the strips by a W filament. In order to improve the electrical contacts and have good reproducibility, a double looped spring design was employed. By using this method, we can heat-up free-standing samples to 1400 K. In addition, by using multiple bimetallic strips with the double looped spring designs, regional heating of the sample can be achieved.
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