Hydrogen effusion from tritiated amorphous silicon

Kherani, Nazir P.; Liu, B.; Virk, K.; Kosteski, Tome; Gaspari, F.; Shmayda, W.T.; Żukotyński, S.; Chen, Kevin P.

doi:10.1063/1.2831495

Cited by 15 publications

(19 citation statements)

References 25 publications

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“…11,19 Tritium effusion experiments were conducted in order to determine the atomic concentration in the samples and its bonding characteristics. 17,18 The detailed experimental setup and procedure have been described previously 17,18 and is briefly described here. The sample was mounted in a 1 L ionization chamber which was purged and then filled with argon gas at 800 Torr.…”

Section: Methodsmentioning

confidence: 99%

“…For all three samples, the low-temperature (LT) peak is located around 370 C and the high temperature (HT) peak is centered around 500 C, which agrees with previous effusion studies on tritiated hydrogenated amorphous silicon (aSi:H:T) prepared by the PECVD process. 2,17,18 The LT peaks suggest the existence of high order silicon tritides and tritium clusters, and the HT peak could be attributed predominantly to the Si-T monotritide bonds. 12,17 By comparing the fractional areas under both HT and LT peaks, it is estimated that around 70% of the tritium in a-Si:H films exists in the form of high order silicon tritides and tritium cluster.…”

Section: A Tritium Contentsmentioning

confidence: 99%

“…The low temperature (LT) peak is around 370 C and the high temperature (HT) one around 500 C. The low temperature hydrogen effusion is usually considered to be limited by surface desorption process, which can be represented by the following surface desorption rate equation: 18,[29][30][31] …”

Section: B Free Energy Of Desorptionmentioning

confidence: 99%

“…2,17,18 The bonding and structural characteristics of tritium in silicon were characterized using thermal effusion measurement. The free energy of tritium desorption in the tritiated silicon is estimated.…”

Section: -mentioning

confidence: 99%

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Self-irradiation enhanced tritium solubility in hydrogenated amorphous and crystalline silicon

Liu¹,

Chen²,

Kherani³

et al. 2011

Journal of Applied Physics

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Experimental results on tritium effusion, along with the tritium depth profiles, from hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) tritiated in tritium (T2) gas at various temperatures and pressures are presented. The results indicate that tritium incorporation is a function of the material microstructure of the as-grown films, rather than the tritium exposure condition. The highest tritium concentration obtained is for a-Si:H deposited at a substrate temperature of 200°C. The tritium content is about 20 at. % on average with a penetration depth of about 50 nm. In contrast, tritium occluded in the c-Si is about 4 at. % with penetration depth of about 10 nm. The tritium concentration observed in a-Si:H and c-Si is much higher than the reported results for the post-hydrogenation process. β irradiation appears to catalyze the tritiation process and enhance tritium dissolution in the silicon matrix. The combination of tritium decay and β-induced ionizations results in formation of reactive species of tritium (tritium atoms, radicals, and ions) that readily adsorb on silicon. The electron bombardment of the silicon surface and subsurface renders it chemically active thereby promoting surface adsorption and subsurface diffusion of tritium, thus leading to tritium occlusion in the silicon matrix. Gaussian deconvolution of tritium effusion spectra yields two peaks for a-Si:H films tritiated at high temperature (250°C), one low temperature (LT) peak which is attributed to tritiated clusters and higher order tritides, and another high temperature peak which is attributed to monotritides. Activation energy of 2.6–4.0 eV for the LT peak was found.

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Section: Methodsmentioning

confidence: 99%

Section: A Tritium Contentsmentioning

confidence: 99%

Section: B Free Energy Of Desorptionmentioning

confidence: 99%

Section: -mentioning

confidence: 99%

See 2 more Smart Citations

Self-irradiation enhanced tritium solubility in hydrogenated amorphous and crystalline silicon

Liu¹,

Chen²,

Kherani³

et al. 2011

Journal of Applied Physics

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“…The high-pressure tritium exposure apparatus used in this experiment is described elsewhere. 8 To study the stability of the tritiatied ScT x film, a thermal effusion measurement 10,11 was performed. Effusion data showed tritium outgassing from the samples beginning at approximately 250°C, the tritium loading temperature, while the majority of tritium evolution occurred near 600°C.…”

mentioning

confidence: 99%

Betavoltaics using scandium tritide and contact potential difference

Liu

Chen

Kherani

et al. 2008

Applied Physics Letters

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Tritium-powered betavoltaic micropower sources using contact potential difference ͑CPD͒ are demonstrated. Thermally stable scandium tritide thin films with a surface activity of 15 mCi/ cm 2 were used as the beta particle source. The electrical field created by the work function difference between the ScT film and a platinum or copper electrode was used to separate the beta-generated electrical charge carriers. Open circuit voltages of 0.5 and 0.16 V and short circuit current densities of 2.7 and 5.3 nA/ cm 2 were achieved for gaseous and solid dielectric media-based CPD cells, respectively. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2887879͔Recently, miniaturized radioisotope micropower sources have drawn significant attention because of their potential of providing a long-term energy solution for niche low-power consuming microsystems for a range of applications including exploration and surveillance. 1-6 A number of nuclear-toelectrical energy conversion integrations, which had been investigated previously, are receiving renewed attention and novel materials and modern microfabrication techniques are being introduced. 1,3 In recent years, a series of studies have been reported on betavoltaics employing semiconductor pn junction using materials such as amorphous silicon, 2 porous silicon, 4 silicon carbide, 5,6 and gallium arsenide/nitride. 1 The efficiency and longevity of these battery structures rely on high-quality pn junctions, which are often susceptible to radiation damage and lack structural self-healing resiliency.One simple method of converting the kinetic energy of ionizing radioemissions into electrical energy is to utilize a contact potential difference ͑CPD͒ device produced from materials with dissimilar work functions. An appropriate dielectric medium, in the form of a thin film, gas, or liquid, is sandwiched between the two dissimilar electrodes. An ionizing radiation source, dispersed within the dielectric medium or included in an electrode, provides the energy source for electron-ion pair generation. Charge carriers are separated by the built-in electric field, created by the contact potential difference of the electrodes, generating current in an external load. A CPD-based micropower source is relatively simple to implement and can be integrated for on-chip applications.Tritium, a radioisotope of hydrogen, is a good candidate for betavoltaic applications given its benign radiation characteristics, its relatively long half-life of 12.3 years, and availability. 2,4,7,8 Tritium is a pure beta emitter producing energetic electrons with an average energy of 5.7 keV and a maximum energy of 18.6 keV. Considering that the threshold electron energy for disruption of the silicon lattice due to knock-on collisions is 20 keV, 9 tritium decay beta particles pose little radiation damage concern for on-chip energy conversion devices. These factors make tritium an appealing power source for on-chip applications. Tritium in the gaseous form has been used in self-power lighting and in betavoltaic ...

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Hydrogen Effusion Experiments

Beyer¹,

Einsele²

2011

Advanced Characterization Techniques for Thin Film Solar Cells

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Hydrogen effusion from tritiated amorphous silicon

Cited by 15 publications

References 25 publications

Self-irradiation enhanced tritium solubility in hydrogenated amorphous and crystalline silicon

Self-irradiation enhanced tritium solubility in hydrogenated amorphous and crystalline silicon

Betavoltaics using scandium tritide and contact potential difference

Hydrogen Effusion Experiments

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