An ice lithography instrument

We describe the design of an instrument that can fully implement a new nanopatterning method called ice lithography, where ice is used as the resist. Water vapor is introduced into a scanning electron microscope (SEM) vacuum chamber above a sample cooled down to 110 K. The vapor condenses, covering the sample with an amorphous layer of ice. To form a lift-off mask, ice is removed by the SEM electron beam (e-beam) guided by an e-beam lithography system. Without breaking vacuum, the sample with the ice mask is then transferred into a metal deposition chamber where metals are deposited by sputtering. The cold sample is then unloaded from the vacuum system and immersed in isopropanol at room temperature. As the ice melts, metal deposited on the ice disperses while the metals deposited on the sample where the ice had been removed by the e-beam remains. The instrument combines a high beam-current thermal field emission SEM fitted with an e-beam lithography system, cryogenic systems, and a high vacuum metal deposition system in a design that optimizes ice lithography for high throughput nanodevice fabrication. The nanoscale capability of the instrument is demonstrated with the fabrication of nanoscale metal lines.     

An ultrahigh vacuum fast-scanning and variable temperature scanning tunneling microscope for large scale imaging

We describe the design and performance of a fast-scanning, variable temperature scanning tunneling microscope (STM) operating from 80 to 700 K in ultrahigh vacuum (UHV), which routinely achieves large scale atomically resolved imaging of compact metallic surfaces. An efficient in-vacuum vibration isolation and cryogenic system allows for no external vibration isolation of the UHV chamber. The design of the sample holder and STM head permits imaging of the same nanometer-size area of the sample before and after sample preparation outside the STM base. Refractory metal samples are frequently annealed up to 2000 K and their cooldown time from room temperature to 80 K is 15 min. The vertical resolution of the instrument was found to be about 2 pm at room temperature. The coarse motor design allows both translation and rotation of the scanner tube. The total scanning area is about 8 x 8 microm(2). The sample temperature can be adjusted by a few tens of degrees while scanning over the same sample area.     

A setup for thermodesorption measurements

An ultrahigh-vacuum setup for studying the interaction of ions with a solid by the thermodesorption spectroscopy method has been developed. The residual pressure achieved in the setup after heating is <2 × 10⁻⁷ Pa (the main component of the residual gas is H₂). A sample suspended by two tungsten wires is inserted into the main vacuum chamber through a lock chamber. The sample is heated by thermal radiation from the heater from room temperature to 1600–1700 K. The main features of the setup, the experimental technique, and the calibration of desorption flows are discussed. Examples of results obtained on the setup are presented.     

Senftleben-Beenakker thermal conductivity effect apparatus

An apparatus for measuring the influence of magnetic fields on the thermal conductivity of gases, the Senftleben-Beenakker effect, is described. Conventional 'cold finger type' cooling with appropriate cryogenic fluids is utilized with a helium exchange gas chamber to establish the general temperature level of the cell holder. Automatic temperature control of the trim heater maintains the desired temperature to +/-10(-3) degrees C in the 77-300 K range. A concentric cylinder cell adaptable for use with either conventional electromagnet or superconducting solenoid is described. The use of thin Mylar polyester film end seals minimizes cell 'end effect' corrections and provides a resolution of 5x10(-6) in gas thermal conductivity.     

Compact cryogenic system with mechanical cryocoolers for antihydrogen synthesis

We have developed a compact cryogenic system which cools a vacuum chamber housing multi-ring trap electrodes (MRTs) of an antihydrogen synthesis trap using mechanical cryocoolers to achieve background pressure less than 10(-12) Torr. The vacuum chamber and the cryocoolers are thermally connected by copper strips of 99.9999% in purity. All components are installed within a diametric gap between the MRT of phi108 mm and a magnet bore of phi160 mm. An adjusting mechanism is prepared to align the MRT axis to the magnet axis. The vacuum chamber was successfully cooled down to 4.0 K after 14 h of cooling with heat load of 0.8 W.     

Thermal property of insulating material at cryogenic temperature

The thermal property of insulation material is essential in developing high temperature superconductor (HTS) devices operating at around liquid nitrogen temperature. Unlike metallic materials, nonmetallic materials have a thermal resistance; therefore, accurate estimate of the heat flow is difficult in the case of nonmetallic materials. In this study, a precise instrument is developed for measuring the thermal property of insulating materials over a temperature range of 30 K to approximately the room temperature by using a cryocooler. The cold head of the cryocooler is thermally anchored to the thermal link and used to cool the apparatus to a desired temperature. The temperature distribution in specimen is measured with respect to the supplied heating power, from which the thermal conductivity is calculated and compared with published data for accuracy confirmation. The effective thermal conductivity of polypropylene laminated paper (PPLP) is presented and the trend in the behavior of conductivity near liquid nitrogen temperature is also discussed.     

High temperature Seebeck coefficient and resistance measurement system for thermoelectric materials in the thin disk geometry

A versatile apparatus to measure the cross-plane Seebeck coefficient and the resistivity of bulk samples shaped as disks or thin plates, over a temperature range of 300 K-620 K with possible extension to higher temperatures, is presented. It is constructed from readily available equipment and instrumentation with parts that are easily manufactured. The Seebeck coefficient is measured over an average region of the sample under steady-state conditions. The sample resistance is measured using a four-point alternating current method and scaled to room temperature measurements with known geometry to calculate resistivity. A variety of sample shapes are supported. Most importantly, the support of the thin disk geometry allows for the very same samples to be used in a laser flash instrument. The design allows for rough vacuum, high vacuum, or purging with inert gases in the sample chamber. Measurements on thermoelectric ZnSb and a Ni reference material are presented.     

A Vacuum High-Temperature Electric Furnace for Investigating Thermal Properties of Materials

A vacuum electric furnace for investigating thermal properties of materials at temperatures of up to 2500°C was developed and tested. The furnace allows experimental studies of the heat conduction of both liquid and solid materials and measurements of the temperature and heat of phase transitions. It can be used to smelt and cake metals and alloys in vacuum or in an inert-gas medium. The heater is made of a graphite tube with special slots for increasing its resistance. The electric power is supplied from an ОСУ-40 step-down transformer. The temperature in the heated zone is controlled and monitored with an РТЭ-4.1 digital temperature controller connected to a computer. The power consumed by the furnace is no higher than 20 kW, and the volume of the working chamber is 0.3 L. The time for reaching the maximum temperature is at most 30 min.     

Polarization Pyrometry of Layered Semiconductor Structures under Conditions of Low-Temperature Technological Processes

Principal issues of using pyrometry for temperature monitoring in low-temperature processes in the technology of production of semiconductor structures are considered by an example of growing mercury–cadmium–telluride (MCT) layers on the GaAs substrate by the method of molecular beam epitaxy. Optical and thermophysical models are proposed to describe the processes of radiant heat transfer in a vacuum chamber. Based on these models, it is demonstrated that radiation from the heater and the signal reflected from the chamber walls, which are comparable in magnitude with the measured radiation emitted by the sample, should be taken into account in interpreting data measured by a pyrometer. Methods of useful signal identification are found. Experiments on temperature measurement by a pyrometer mounted on the MCT growth chamber are performed. Results of these experiments are in good agreement with theoretical predictions.     

A temperature and pressure controlled calibration system for pressure sensors

A data acquisition and experiment control system has been developed to characterize and calibrate prototype pressure sensors capable of operation in a cryogenic environment. The system consists of: a personal computer for acquisition of sensor output voltage, sensor operating parameters, and data processing including numerically derived corrections for sensor thermal offset, sensitivity variations, and thermal errors; an environmental chamber capable of controlling temperature to within 1 °C over a −184 °C to 220 °C range; a pressure standard capable of generating pressures to within 1 part in 100,000 over a 0 to 344.74 kPa range; and a data logger for recording outputs from system multimeters, precision resistance temperature devices, thermocouples, and power supplies. The system utilizes a modified, commercially available interface board to allow the demultiplexing, digitation, and input of remotely multiplexed, pulse amplitude modulated pressure signals from pressure sensor arrays to the PC bus. System software is discussed and includes: sensor data acquisition, algorithms for numerically derived thermal offset and sensitivity correction, and operation of the environmental chamber and pressure standard.     

模糊人工神经网络在真空管太阳能热水器热效率预测中的应用

热效率是设计真空管太阳能热水器时的重要参数。本文综合应用模糊数学和神经网络的知识构建了一个模糊神经网络模型。根据真空管太阳能热水器的真空管支数、真空管长度、集热面积、容水量等物性参数和初始水温、平均环境温度、辐照量和风速等环境参数，预测太阳能热水器的热效率。结果表明，该方法速度快，结果较准确，为真空管太阳能热水器的设计提供了一个新的辅助手段。     

Irradiation of cryogenic temperature sensors by gamma dose of 1 MGy

This article presents results of investigations of the cryogenic thermometers which can operate under high radiation environment. To clarify the temperature shifts due to gamma irradiation up to 1 MGy, the platinum (two types), carbon-glass, and TVO temperature sensors have been tested. Before the irradiation run, the selected sensors were calibrated and a series of experiments was carried out under irradiation of the sensors at 77.3 and 293 K when their readings were taken in situ. Afterwards, the postirradiation evolution (short and long time) of the sensors was measured at 4.2, 77.3, and 293 K. The results, depending on the type of the sensor, can be optimistic or pessimistic. Some comparisons with analogous data for fast neutron treatment have also been made.     

Robotic reconnaissance platform. I. Spectroscopic instruments with rangefinders

In this paper, basic principles of the design and implementation of a portable, multi-functional scientific instrument, operating from a robotic reconnaissance mobile platform are discussed. The current version of the instrument includes a multi-gas laser sensor, multi-functional spectrometer, isotopes identifier, cameras, and rangefinder. An additional set of sensors monitors temperature, pressure, humidity, and background radiation. All components are installed on a mini-robotic platform, which provides data acquisition, processing, and transmittance. The design focuses on the development of calibration-free, reliable, low power-consumption devices. To create a highly survivable, accurate, and reliable instrument, a concept of an inhomogeneous sensory network has been developed. Such a network combines non-identical sensors and provides cross-use of information received from different sensors to describe environmental conditions, to choose appropriate algorithms of data processing, and to achieve high accuracy gas-concentration measurements. The system uses the same lasers to operate different optical devices such as sensors, rangefinders, spectrometers, and isotopes identifiers. Among the innovative elements described in this paper, are a calibration-free, laser multi-gas sensor with range-finding option; a high signal/noise ratio transmittance spectrometer; a single-frequency laser with nano-selector; and low repetition-rate femtosecond fiber lasers operating in near- and middle- infrared spectral ranges. New detailed analyses of absorption spectroscopy theoretical approximations made it possible to achieve high-accuracy gas-concentration measurements with miniature optical sensors.     

膜盒式压力传感器的创新设计原理与工程应用

弹性膜盒作为压力式传感器大量应用在石油化工、仪表、航空等领域,通过研究发现了弹性膜盒不同于上述传统应用方法的新特性,在大量试验数据的基础上,提出了一种创新设计理论与方法,成功地将其作为温度传感器应用于某温度控制继电器。采用该原理和方法设计制造的新型温度传感器大批量生产应用于洗衣机、电热水器等家用电器,证明具有极佳的工作精度、重复性、稳定性与可靠性,为弹性膜盒开辟了一种新的应用领域。     

Development of a new apparatus for ultrasonic vibration-assisted glass hot embossing process

A new apparatus for an ultrasonic vibration-assisted glass hot embossing process has been developed. The upper die constitutes the ultrasonic vibrating device, and a cooler is provided to protect the transducer from the high operating temperatures. An ultrasonic horn originally designed for use at room temperature was modified to ensure correct operation of ultrasonic vibrating device for high temperature use. Because the load cell is located inside a vacuum chamber, the detection of the force applied to the glass during the forming process is not significantly impacted by external forces, and thus, a precise force history of the forming glass can be obtained. Flat hot embossing experiments were performed to investigate the effect of ultrasonic vibration on the amount of force required during forming, and Fresnel structure hot embossing experiments were then conducted to investigate the improvement in molding accuracy gained through ultrasonic vibration. The experimental results are taken to validate the manufacturing potential of the developed apparatus and the improvement in formability achieved by applying ultrasonic vibration.     

Cryogenic probe station for on-wafer characterization of electrical devices

A probe station, suitable for the electrical characterization of integrated circuits at cryogenic temperatures is presented. The unique design incorporates all moving components inside the cryostat at room temperature, greatly simplifying the design and allowing automated step and repeat testing. The system can characterize wafers up to 100 mm in diameter, at temperatures <20 K. It is capable of highly repeatable measurements at millimeter-wave frequencies, even though it utilizes a Gifford McMahon cryocooler which typically imposes limits due to vibration. Its capabilities are illustrated by noise temperature and S-parameter measurements on low noise amplifiers for radio astronomy, operating at 75-116 GHz.     

低气压下板式电加热器换热性能的研究

板式电加热器是一种常用的供热设备，其电热板的温度有一定的限制。随着海拔高度的增加，大气压力的降低会引起空气密度的减小，根据传热学理论的分析，将导致自然对流换热系数h下降，即电加热器的换热性能下降。按照Kreith和Gryzagoridis提出的经验公式，若仅考虑气压的影响，在唐古拉山垭口处竖平壁的自然对流换热系数h仅为海平面处的73％。如果板式电加热器的电功率不变时，电热板的温度就会升高。低压箱内的试验结果证明了这一趋势。     

Low temperature investigations on frictional behaviour and wear resistance of solid lubricant coatings

The tribological characteristics of polymer-based solid lubricant coatings under frictional stressing in vacuum at 293, 120 or 77 K were studied. Vacuum-friction apparatus with cryogenic pumps and low-temperature tribometer designed at SR&DB of ILTP&E was used for sliding tests. It was found that the coefficient of friction is somewhat higher at low than at room temperatures. The effect of temperature decrease on the wear life of solid lubricant coatings is ambiguous and determined by the direction of changes in physical and mechanical characteristics of a solid lubricant coating under cooling and by the rate of the process of a binder tribodestruction.     

A simple device for dielectric spectroscopy of polymers with temperature regulation close to 300 K based on a Peltier junction

We present a simple thermostat device for performing dielectric spectroscopy measurements on polymers close to their glass transition temperature. By using a vacuum chamber containing a Peltier junction with its regulator, we show that a very simple setup yields a temperature accuracy which is good enough for accurate studies of polymer dielectric properties. This technique is also more cost effective than standard setups using cryogenic fluids.