Ultrahigh Vacuum Devices Research Articles

Analysis of the change in the composition of the CdTe surface upon implantation of О_2^+ ions and subsequent annealing

The methods of implantation of О_2^+ ions into a single-crystal CdTe/Mo(111) film followed by annealing at Т=800 K for 30 min resulted in the obtained CdTeO3 film. Ion implantation, heating, and investigation of the composition, density of state of valence electrons, and parameters of energy bands are carried out in the same ultra-high vacuum device (10-7 Pa). The surface morphology and crystal structure of the oxide are studied using standard scanning electron microscopy and high-speed electron diffraction setups. It has been established that in the valence band of the CdTeO3 film there is a 3rd maximum due to the excitation of electrons from 5s Cd electrons and 2p O electrons and bending 5s Cd + 2pO electrons. Based on the Eg data, it is concluded that quantum size effects are not detected in the case of CdTeO3 films with a thickness of ≥ 30 Å.

Improved initial drop in operational lifetime of blue phosphorescent organic light emitting device fabricated under ultra high vacuum condition

A blue phosphorescent organic light emitting device fabricated under the ultra high vacuum (UHV) condition of 6.5 × 10−7 Pa decreases the initial luminance drop upon lifetesting under a constant dc current of 15 mA/cm2 by 3 times compared to a device fabricated under a high vacuum (HV) condition of 7.6 × 10−6 Pa resulting in a 23% increase in half lifetime. We calculate a water content of 10−4 mol. % in the UHV device emissive layer (EML) and 10−2 mol. % in the HV device EML. We discuss the effects of water on luminance loss and voltage rise for the devices.

An ultrahigh vacuum device for measuring the conductivity of surface structures by a four-probe method based on a closed-cycle refrigerator

An ultrahigh vacuum device for measuring the conductivity of surface structures based on a closed-cycle refrigerator is described. The device allows measurements of the conductivity of surface atomic structures as a function of the temperature (in the range 22—300 K) and electric field. The circuit for conductivity measurements allows operation with contact resistances of up to 1010 Ω and currents as low as 10-13A. The operation of the device is demonstrated by an example of measuring the conductivity of a clean reconstructed Si(111)7 - 7 surface.

Ultrasensitive leak detection during ultrahigh vacuum evacuation by quadrupole mass spectrometer

One must do ultrasensitive leak detection during ultrahigh-vacuum (UHV) evacuation, especially just before the device is sealed off from the vacuum system, to guarantee the longevity of the sealed high-vacuum or even UHV devices with small volume. A quadrupole mass spectrometer (QMS) with an UHV evacuation system can be used under accumulation mode to do the testing. Possible accumulate modes, as well as their advantages and shortcomings, are studied experimentally and discussed in this paper. We found that the opening action of the metal valve during accumulation mode always severely affects the height of the peak indicated by QMS and causes considerable errors. If we determine the leak rate by the peak area instead of the peak height, the situation is much improved. This method has proven quite useful in ensuring the tightness quality for complex sealed UHV devices with small volumes. Ultrasensitive leak detection has been carried out for such real evacuating devices, and a leak rate of 2×10−14Pa∙m3∕s was detected, which is far lower than its dynamic mode and the detection limit of the current advanced commercial leak detectors.

Gas desorption from a stainless-steel surface in ultrahigh vacuum devices

Degassing of stainless-steel surface in a vacuum system with high unit pumping speed was investigated. Possibility of efficient surface outgassing at 400 K has been confirmed. An attempt to describe phenomena connected with hydrogen desorption from surface at 300 K is presented.

Steady state behavior of a multipolar plasma device

A low pressure discharge plasma, with magnetic multipolar confinement, is produced in a cylindrical ultrahigh vacuum device. The device has been specially designed to allow both moving Langmuir probe measurements and laser induced fluorescence diagnostic for the plasma ions. It is well suited to explore the sheaths region in a bounded plasma and to study wave and turbulence in a laboratory plasma. The main characteristics of the experimental setup and of the produced plasma are described.

Joining of Alumina Ceramics to Metal by Solution Metallization Process

Ultra high vacuum (UHV) joining between alumina ceramics and metal is the key to the success of many devices used in modern technology. The conventional processes like high-temperature Sintered Metal Powder Process (SMPP) and active metal brazing are capital intensive and are not suitable for custom made items where the requirement of the product is small. In such cases, solution metallization is an easy and economic alternative. Over a decade we have perfected this method for the fabrication of high-tech UHV device like Linac. Though this process requires only 1050°C vis-a-vis 1500°C for SMPP, performance-wise ceramic to metal seals made by solution metallization are comparable to or in some respect better than those obtained by other established processes. The bond quality is dependent upon several process parameters. A systematic investigation has been performed to find out the effect of different process parameters like pretreatment of ceramic, paint composition, metallization temperature, time and at...

Effect of the environment on the high temperature embrittlement of inconel 718

The oxygen embrittlement of Inconel 718 has been investigated by means of hot tensile tests in an ultrahigh vacuum device. It has been shown that a pre-oxidizing treatment (200 h at 923 K) does not induce a major effect on the further mechanical behaviour of tensile samples when tested at 923 K in ultrahigh vacuum. In addition, a transition of the failure mode has been determined for an O 2 pressure as low as 10 −1 Pa. Possible interactions between external oxygen and internal hydrogen dissolved in the alloy have also been studied using hot tensile tests on either hydrogen-charged or hydrogen-degassed samples. Both types of sample exhibit the same mecahnical behaviour. Hot tensile tests under pure CO have also been carried out. The results obtained seem to indicate that the first stage of the oxidation process in the grain boundaries before Cr 2O 3 formation plays an important role in the embrittlement mechanism of this alloy.

555. Glass bellows manometer for ultrahigh vacuum devices for a range of 1 to 760 torr.: LA Boschi and EA Garcia, Rev Sci Instrum, 38 (11), 1967, 1610–1611

555. Glass bellows manometer for ultrahigh vacuum devices for a range of 1 to 760 torr.: LA Boschi and EA Garcia, Rev Sci Instrum, 38 (11), 1967, 1610–1611

Glass Bellows Manometer for Ultrahigh-Vacuum Devices for a Range of 1 to 760 Torr

A thoroughly bakeable Pyrex glass bellows manometer has been made. It has the precision of a mercury one, and also the advantages of low cost and easy construction. The bellows displacement is measured photoelectrically.