No abstract

Niobium nitride-niobium nitride Josephson tunnel junctions have been fabricated using amorphous magnesium oxide (a-MgO) films as barriers. These junctions have excellent tunneling characteristics. For example, a large gap voltage (Vg=5.1 mV), a large product of the maximum critical current and the normal tunneling resistance (IcRn=3.25 mV), and a small subgap leakage current (Vm=45 mV, measured at 3 mV) have been obtained for a NbN/a-MgO/NbN junction. The critical current of this junction remains finite up to 14.5 K.

We have improved the quality of Nb/Al-AlOx/Nb Josephson junctions and obtained the most excellent junction characteristics ever obtained for all refractory Josephson junctions. The Vm values (the product of the critical current and the subgap resistance measured at 2 mV) are 88 mV at the critical current density Ij =500 A/cm2 and 72 mV at Ij =1000 A/cm2. The Vm values are larger than 40 mV up to Ij of 2400 A/cm2. The high Vm values are important to obtain the low subgap leakage current and not to reduce the transfer current to the load in Josephson circuit. These characteristics have been achieved by improving the quality of the Nb film and optimizing the Al thickness. We have also confirmed that Ij can be controlled by both the oxidation pressure and time in the range of 40–4600 A/cm2.

Industries from agriculture to petrochemistry have found near infrared (NIR) spectroscopic analysis useful for quality control and quantitative analysis of materials and products. The general chemical, polymer chemistry, petrochemistry, agriculture, food and textile industries are currently using NIR spectroscopic methods for analysis. In this study, we developed a portable NIR instrument for the non-destructive testing of products in the field, which has resulted in an instrument for commercial sale and use. The instrument consists of a light source, a polychromator, a wave-guide (optical fibre bundle) and a data processing unit. We tested the performance of the portable NIR instrument in determining the sugar content of apples. The performance was also examined at full width at half maximum (FWHM) of the spectrum. The difference in the absorption of quartz and plastic fibres in the NIR was also compared. The sugar content measurements were confirmed by a high correlation to the Brix value of the apples, and the calibration showed the accuracy of the instrument in practice. Application of this instrument to fruits and vegetables other than apples was explored.

The reactive mechanism of rf reactive sputtering has been investigated by mass spectrometry in an rf diode sputtering system. The result indicates that the gettering action of the sputtered active atom deposits influences the progress of reactive sputtering in addition to the target reaction. A model, taking the gettering action into consideration, is presented for the reactive sputtering of a metal. This model shows that an abrupt steplike decrease in the sputtering rate may occur at a definite partial pressure of a reactive gas p* in the plasma. The pressure p* is determined from the gettering rate of the sputtered deposits relative to the throughput of the reactive gas. The value of the pressure p* calculated on this model is in good agreement with the experimental results.