Using Ultrathin Parylene Films as an Organic Gate Insulator in Nanowire Field-Effect Transistors.

We report the development of nanowire field-effect transistors featuring an ultrathin parylene film as a polymer gate insulator. The room temperature, gas-phase deposition of parylene is an attractive alternative to oxide insulators prepared at high temperatures using atomic layer deposition. We discuss our custom-built parylene deposition system, which is designed for reliable and controlled deposition of <100 nm thick parylene films on III-V nanowires standing vertically on a growth substrate or horizontally on a device substrate. The former case gives conformally coated nanowires, which we used to produce functional Ω-gate and gate-all-around structures. These give subthreshold swings as low as 140 mV/dec and on/off ratios exceeding 103 at room temperature. For the gate-all-around structure, we developed a novel fabrication strategy that overcomes some of the limitations with previous lateral wrap-gate nanowire transistors. Finally, we show that parylene can be deposited over chemically treated nanowire surfaces, a feature generally not possible with oxides produced by atomic layer deposition due to the surface "self-cleaning" effect. Our results highlight the potential for parylene as an alternative ultrathin insulator in nanoscale electronic devices more broadly, with potential applications extending into nanobioelectronics due to parylene's well-established biocompatible properties.

Electronic transport in conducting polymer nanowire array devices.

We report on the temperature dependent conductivity and current-voltage (I-V) properties of novel polyaniline nanowire array devices. Below 60 K, I-V measurements show a transition to non-linear behaviour, leading to the onset at 30 K of a threshold voltage, for potentials below which little current flows. By considering an intrinsic morphology of small conducting regions separated by tunnel junctions, we show that charging of the conducting regions leads to Coulomb blockade effects that can account for this behaviour.

Formaldehyde toxicity. Part II. Review of acute and chronic effects on health.

Inhaled formaldehyde has acute effects on the respiratory tract, central nervous system, skin and eyes and also chronic effects on the respiratory tract, particularly on pulmonary function. Formaldehyde has also been associated with adverse reproductive and mutagenic effects, and there is evidence of carcinogenic effects from two important animal studies. Some data, largely indirect, suggest a carcinogenic risk for man. The reactions of some international scientific bodies to the accumulated data are noted, and steps taken by a number of countries to control formaldehyde exposure in the workplace and other environments are discussed.

Formaldehyde toxicity. Part I. Occupational exposure and a report of 5 cases.

Formaldehyde is ubiquitous in the occupational, domestic and general environment, and in manufactured and consumer goods. The clinical and radiological findings in 5 shop employees exposed to formaldhyde are presented. Two features are of interest: (i) 1 of the workers developed vomiting, a symptom previously unreported in adults exposed to formaldehyde; and (ii) all 5 victims developed turbinate swelling, apparent clinically and radiologically. The swelling was marked, causing obstruction of the nasal passages, and persisted for some time after most of the sources of exposure had been dealt with. This phenomenon is also previously undocumented.

Immunotherapy with BCG vaccine in 30 cases of mesothelioma.

Thirty patients with malignant pleural mesothelioma who underwent BCG vaccine immunotherapy are presented. There was an improved survival rate, compared with patients treated symptomatically only. Techniques of therapy are detailed and the importance of 'tumour load' reduction and prolonged injection schedule, is stressed.

Pneumoconiosis in non-mining industries on the Witwatersrand.

Two hundred and eighty-seven patients referred to the National Research Institute for Occupational Diseases with suspected pneumoconiosis are recorded. The patients are classified according to the type of dust to which they were exposed, and by occupation or industry. Radiological evidence of pneumoconiosis according to ILO/UICC classification is the only acceptable basis for compensation at present, and the number of patients so diagnosed is also given. None of these figures show the true distribution and incidence of pneumoconiosis as a form of occupational disease on the Witwatersrand. They only indicate the presence of pneumoconiosis not associated with mining and reflect a wide range of occupations.