Vacuum properties of palladium thin film coatings

There are several contributions to the gas load of a system of which often the most important is outgassing. Adsorption occurs via two main processes, physisorption and chemisorption, and can be described using five (or six) classifying isotherms. Outgassing is the result of desorption of previously adsorbed molecules, bulk diffusion, permeation and vapourisation. Looking at the desorption rate, pumping speed and readsorption on surfaces, the net outgassing of the system can be calculated. There is significant variation in measured outgassing rates between different materials but also between published rates for the same materials, in part due to the number of different methods used to measure outgassing. This article aims to review the outgassing process, outgassing rates, measurement methods and techniques that can be used to reduce the outgassing of a system.

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“…Experimental data from Benvenuti et al [29,30,[54][55] showing the pressure of the vacuum system during activation of several NEG coatings.…”

Section: Oxidation and Bakingmentioning

confidence: 99%

A Review of Outgassing and Methods for its Reduction

Grinham

Chew

2017

Appl. Sci. Converg. Technol.

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“…Palladium coating has also been used to promote hydrogen absorption by bulk samples of: niobium and tantalum [18], vanadium [19], magnesium [20], and titanium [21]. In addition, vacuum deposited palladium coatings have been used on non-evaporable getter materials, [22], to create composite getters that will absorb hydrogen to very low pressures without a thermal activation step. The mechanism(s) by which palladium promotes bulk absorption are only partially understood and tend to differ between materials.…”

Section: Tablesmentioning

confidence: 99%

Titanium tritide radioisotope heat source development : palladium-coated titanium hydriding kinetics and tritium loading tests.

Shugard¹,

Walters²,

Blarigan

2012

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We have found that a 180 nm palladium coating enables titanium to be loaded with hydrogen isotopes without the typical 400-500 C vacuum activation step. The hydriding kinetics of Pd coated Ti can be described by the Mintz-Bloch adherent film model, where the rate of hydrogen absorption is controlled by diffusion through an adherent metal-hydride layer. Hydriding rate constants of Pd coated and vacuum activated Ti were found to be very similar. In addition, deuterium/tritium loading experiments were done on stacks of Pd coated Ti foil in a representative-size radioisotope heat source vessel. The experiments demonstrated that such a vessel could be loaded completely, at temperatures below 300 C, in less than 10 hours, using existing department-of-energy tritium handling infrastructure.4

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“…The most common and technically accepted way to maintain a controlled ambient environment in a hermetically sealed MEMS device is to use a NEG capable of chemically absorbing active gasses, such as H 2 O, CO, CO 2 , O 2 , N 2 and H 2 . However, the conventional bulk or sheet getters having the property of high pumping speed even at room temperature, could not be used in these minimizing MEMS devices due to the restricted space [5][6][7]. It is urgently required to develop the highly porous thin-film-type getters with several μm thickness for the applications of MEMS vacuum devices.…”

Section: Introductionmentioning

confidence: 99%

ZrCoCe Getter Film Solution for Under Controlled Atmosphere MEMS Packaging

Xu¹,

Cui²,

Cui³

et al. 2015

Proceedings of the International Conference on Advances in Energy, Environment and Chemical Engineering

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Abstract. In order to specifically support the technology trend of increased miniaturization of Micro Electro Mechanical Systems (MEMS) devices, highly porous ZrCoCe non-evaporable getter (NEG) film has been produced by DC magnetron sputtering from a preformed ZrCoCe alloy target. The porous film is composed of columnar crystals, which is further built up with assembled ZrCoCe amorphous or nanocrystalline grains. Gas sorption investigation shows that this film can be activated at low temperature and exhibits excellent stable sorption characteristics. Sorption properties can be further improved with elevating the activation temperatures due to the microstructure modification. The capability of ZrCoCe films withstanding wafer physical or chemical cleaning processes is investigated, indicating their compatibility with MEMS vacuum packaging and the appropriate way to store them. IntroductionDiscrete packages are very critical to assure an excellent hermeticity in many MEMS devices to perform their basic functions properly and to enhance their reliability by keeping these devices away from the harmful external environment [1][2][3][4]. With the technology trend of increased miniaturization of MEMS devices, maintaining the needed vacuum level in such packages for the entire MEMS device life becomes a real technical challenge due to the very high surface to volume ratio [1]. The most common and technically accepted way to maintain a controlled ambient environment in a hermetically sealed MEMS device is to use a NEG capable of chemically absorbing active gasses, such as H 2 O, CO, CO 2 , O 2 , N 2 and H 2 . However, the conventional bulk or sheet getters having the property of high pumping speed even at room temperature, could not be used in these minimizing MEMS devices due to the restricted space [5][6][7]. It is urgently required to develop the highly porous thin-film-type getters with several μm thickness for the applications of MEMS vacuum devices.Ti, Ti-Zr-V, Zr-V-Fe or ZrV 2 are typical NEG film materials, which have been widely studied in sealed-off vacuum technology. Nevertheless, the aforementioned materials may be defined as NEG materials of specific use, and are often described and referred to in patents and technical or commercial bulletins with reference to their use in specific applications [8][9][10]. Zr-Co-rare earth (RE) alloys are specially developed to fulfil some specific integration needs. These alloys are advantageous because they are suitable for general use. they have a relatively low activation temperature 200-500°C, are capable of sorbing a wide variety of gases, and minimize the environmental and safety risks compared with known nonevaporable getter alloys [11].It is known from previous studies that ZrCoRE films have been prepared by RF magnetron sputtering and sorption properties can be improved by optimizing related parameters [12,13]. However, the performance of the above films are too low to fulfil practical applications and mass production. More efficient sorption capacity and higher sta...

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Vacuum properties of palladium thin film coatings

Cited by 51 publications

References 15 publications

A Review of Outgassing and Methods for its Reduction

A Review of Outgassing and Methods for its Reduction

Titanium tritide radioisotope heat source development : palladium-coated titanium hydriding kinetics and tritium loading tests.

ZrCoCe Getter Film Solution for Under Controlled Atmosphere MEMS Packaging

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