Collisionless expansion of pulsed rf plasmas

Schröder, T.; Grulke, O.; Klinger, T.; Boswell, Roderick; Charles, Christine

doi:10.1088/0022-3727/47/5/055207

Cited by 3 publications

(16 citation statements)

References 20 publications

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“…There are reportedly only a limited number of types of such characteristic clusters. [4] Our spectra (Figure 2 and 4) indicate seven such characteristic clusters to be present in the seed-end wafers after heat treatment at 450 C for 99 h. The multiplication of TDs leads to an increased injection level of free charge carriers in the conduction band upon excitation. This leads to increased signal also from the direct BB recombination mechanism.…”

Section: Spectral Pl Response and Images Of Thermally Annealed Tail-ementioning

confidence: 99%

“…Consensus at present time is the existence of a distinct set of TD that have a common core, into which oxygen agglomerates. [7] The size of these clusters has been proposed to be affected by the annealing time, [4] and each type of TD will introduce an energy state associated with two electrons in the bandgap and thus act as a double donor.…”

Section: Doi: 101002/pssa201900884mentioning

confidence: 99%

“…As an example, high concentrations of carbon have shown an inhibiting effect on the formation of TD, proposed to be due to creation of CO complexes. [4] There are conflicting reports on which role selfinterstitials or vacancies play in the structure, but a more recent study done by Voronkov et al showed that higher concentrations of self-interstitials had an enhancing effect on the TD generation rate. [9] Temperatures above 600 C caused the defect leading to TD to disappear, and these temperatures seem to be enough to cause the O i atoms to out-diffuse from their specific centers.…”

Section: Doi: 101002/pssa201900884mentioning

confidence: 99%

“…[1,2] Different TDs are reported to introduce donor states placed at different energy levels within the bandgap of silicon. [3] It has further been suggested that the various types of TD differ in cluster size, and that larger clusters form with a long annealing time at 450 C. [4,5] Photoluminescence (PL) studies have shown that these energy states exist both at a deep and a shallow level in the bandgap. [3] PL emissions that occur due to traps inside the bandgap are categorized as defect-related luminescence (DRL).…”

Section: Introductionmentioning

confidence: 99%

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Spectral Characteristics and Spatial Distribution of Thermal Donors in n‐Type Czochralski‐Silicon Wafers

Olsen

Helander

Mehl

et al. 2020

Physica Status Solidi (a)

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In monocrystalline silicon rich in oxygen, thermal donors are formed at temperatures around 450 °C. These are widely accepted to be electrically active oxygen clusters acting as double donors to the conduction band. Exposure to higher temperatures (650 °C) reportedly eliminates them. Herein, a systematic study of the spatial distribution of thermal donor formation and elimination by heat treatment at 450 and 650 °C in commercial n‐type Czochralski‐silicon wafers with high and low content of interstitial oxygen atoms are reported. Hyperspectral imaging techniques with spectral and spatial resolution are used. Thermal donors form at 450 °C in a ring‐like pattern, significantly enhanced in oxygen‐rich material. The results indicate the formation of at least six different donor clusters, leading to a strong, characteristic spectral response upon photoexcitation. The emission related to direct band‐to‐band recombination (1.100 eV) become systematically stronger upon heat treatment at 450 °C. Subsequent treatment at 650 °C rearrange the spectral response into a single, homogenously distributed, broadband emission with peak energy of 0.767 eV. The emission related to band‐to‐band recombination is significantly reduced. A previously studied emission at 0.807 eV (D1) commonly related to impurities is found, providing evidence that this signal is related to the combination of defects and oxygen.

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Section: Spectral Pl Response and Images Of Thermally Annealed Tail-ementioning

confidence: 99%

Section: Doi: 101002/pssa201900884mentioning

confidence: 99%

Section: Doi: 101002/pssa201900884mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spectral Characteristics and Spatial Distribution of Thermal Donors in n‐Type Czochralski‐Silicon Wafers

Olsen

Helander

Mehl

et al. 2020

Physica Status Solidi (a)

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“…The complexity is thereby increased up to a self consistent simulation of the ignition of a radio frequency (rf) plasma tailored to an existing plasma expansion experiment. 1 In contrast to the ignition with ultra-short laser pulses, [13][14][15]17 the use of the rf source allows for an increase of the spatial dimension of the plasma expansion. This in turn enables the use of a different set of diagnostics such as electrostatic probes and energy analysers.…”

Section: Introductionmentioning

confidence: 99%

Collisionless expansion of pulsed radio frequency plasmas. I. Front formation

et al. 2016

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The dynamics during plasma expansion are studied with the use of a versatile particle-in-cell simulation with a variable neutral gas density profile. The simulation is tailored to a radio frequency plasma expansion experiment [Schr€ oder et al., J. Phys. D: Appl. Phys. 47(5), 055207 (2014)]. The experiment has shown the existence of a propagating ion front. The ion front features a strong electric field and features a sharp plasma potential drop similar to a double layer. However, the presented results of a first principle simulation show that, in general, the ion front does not have to be entangled with an electric field. The propagating electric field reflects the downstream ions, which stream with velocities up to twice as high as that of the ion front propagation. The observed ion density peak forms due to the accumulation of the reflected ions. The simulation shows that the ion front formation strongly depends on the initial ion density profile and is subject to a wave-breaking phenomenon. Virtual diagnostics in the code allow for a direct comparison with experimental results. Using this technique, the plateau forming in the wake of the plasma front could be indirectly verified in the expansion experiment. Although the simulation considers profiles only in one spatial dimensional, its results are qualitatively in a very good agreement with the laboratory experiment. It can successfully reproduce findings obtained by independent numerical models and simulations. This indicates that the effects of magnetic field structures and tangential inhomogeneities are not essential for the general expansion dynamic. The presented simulation will be used for a detailed parameter study dealt with in Paper II [Schr€ oder et al., Phys. Plasma 23, 013512 (2016)] of this series. V

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Collisionless expansion of pulsed radio frequency plasmas. II. Parameter study

et al. 2016

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The plasma parameter dependencies of the dynamics during the expansion of plasma are studied with the use of a versatile particle-in-cell simulation tailored to a plasma expansion experiment [Schr€ oder et al., J. Phys. D: Appl. Phys. 47, 055207 (2014); Schr€ oder et al., Phys. Plasmas 23, 013511 (2016)]. The plasma expansion into a low-density ambient plasma features a propagating ion front that is preceding a density plateau. It has been shown that the front formation is entangled with a wave-breaking mechanism, i.e., an ion collapse [Sack and Schamel, Plasma Phys. Controlled Fusion 27, 717 (1985); Sack and Schamel, Phys. Lett. A 110, 206 (1985)], and the launch of an ion burst [Schr€ oder et al., Phys. Plasmas 23, 013511 (2016)]. The systematic parameter study presented in this paper focuses on the influence on this mechanism its effect on the maximum velocity of the ion front and burst. It is shown that, apart from the well known dependency of the front propagation on the ion sound velocity, it also depends sensitively on the density ratio between main and ambient plasma density. The maximum ion velocity depends further on the initial potential gradient, being mostly influenced by the plasma density ratio in the source and expansion regions. The results of the study are compared with independent numerical studies.

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Collisionless expansion of pulsed rf plasmas

Cited by 3 publications

References 20 publications

Spectral Characteristics and Spatial Distribution of Thermal Donors in n‐Type Czochralski‐Silicon Wafers

Spectral Characteristics and Spatial Distribution of Thermal Donors in n‐Type Czochralski‐Silicon Wafers

Collisionless expansion of pulsed radio frequency plasmas. I. Front formation

Collisionless expansion of pulsed radio frequency plasmas. II. Parameter study

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