Hydrogenation of evaporated amorphous silicon films by plasma treatment

Kaplan, D.; Sol, N.; Velasco, G.; Thomas, P.

doi:10.1063/1.90370

Cited by 117 publications

(16 citation statements)

References 6 publications

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“…After deposition, we applied a hydrogen treatment using hot-wire decomposition in order to compensate for outgassing of hydrogen during the conversion process. [ 18 ] Solar Cell Stack Design : For the solar cells, we built a stack as follows: On 1.1 mm fusion-drawn glass substrate, we sputtered 800 nm Al-doped ZnO as transparent conductive material, [ 19 ] followed by the deposition of a n-i-p layer stack of amorphous silicon with a total thickness between 150 and 200 nm. On top of it, 100 nm Al-doped ZnO were sputtered as the front contact.…”

Section: Methodsmentioning

confidence: 99%

Solution‐Based Silicon in Thin‐Film Solar Cells

Bronger

Wöbkenberg

Wördenweber

et al. 2014

Advanced Energy Materials

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factor of 7. This shows that solution-based silicon is a highly promising candidate for industrial-grade applications of solutionbased semiconductors. Evaluation of Precursors NPS and CPSIn literature, most groups reporting silicon fi lms fabricated from a liquid precursor use a cyclic hydridosilane, namely cyclopentasilane (CPS). We decided to use a branched molecule instead, namely neopentasilane (NPS). The molecular structures of CPS and NPS, as well as the process charts for obtaining solid amorphous silicon (a-Si) layers, are shown in Figure 1 . We characterized the NPS used in our process chain by NMR and by mass spectroscopy, showing the expected fi ngerprints mentioned in literature. [ 4 ] Employing NPS over CPS yields major advantages in processing effi ciency as well as in material quality. In general, branched molecules have a considerably better solubility in organic solvents, because the branches act as spacers, preventing strong interactions between the molecules and enabling better intercalation of solvent molecules. [ 5 ] The NPS material is therefore better soluble than CPS, which leads to improved fi lm homogeneity and uniformity. Moreover, in NMR measurements, we found that the NPS-oligomer bears 70% SiH 3 end groups, in contrast to 1.0% for the CPS-oligomer. Such end groups facilitate the cross-linking of the material to a solid network. Since this process is responsible for the formation of silicon-silicon bonds, we expect a positive effect on the coordination of silicon atoms, resulting in less dangling bonds and improved electronic properties. Until now, we have however not been able to demonstrate differences in nanoscopic amorphous silicon structure between CPS and NPS.Another major advantage of employing NPS instead of CPS lies in the differences in material synthesis. The synthesis of the CPS monomer involves a coupling reaction and subsequent chlorination of diphenyldichlorosilane to obtain decachlorocyclopentasilane. This process produces a large amount of various by-products, which are diffi cult to separate and recycle. However, in the synthesis of NPS, we use catalytic rearrangement of octachlorotrisilane to obtain dodecachloroneopentasilane,

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Section: Methodsmentioning

confidence: 99%

Solution‐Based Silicon in Thin‐Film Solar Cells

Bronger

Wöbkenberg

Wördenweber

et al. 2014

Advanced Energy Materials

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“…35 Exposure to hydrogen plasma at elevated temperatures can completely eliminate the dangling silicon bond signal as detected by ESR. 36 Infrared ͑IR͒-absorption spectral band analysis confirmed that hydrogenated films possess simple Si-H vibrations, demonstrating the danglingbond density was decreased via hydrogen passivation. 36 Thus, the level of hydrogen incorporation in amorphous silicon can serve as a strong indication of the dangling-bond defect density for the material.…”

Section: Discussionmentioning

confidence: 92%

“…36 Infrared ͑IR͒-absorption spectral band analysis confirmed that hydrogenated films possess simple Si-H vibrations, demonstrating the danglingbond density was decreased via hydrogen passivation. 36 Thus, the level of hydrogen incorporation in amorphous silicon can serve as a strong indication of the dangling-bond defect density for the material. Amorphous silicon can be permeated with hydrogen concentrations up to 1 ϫ 10 20 atoms/ cm 3 .…”

Section: Discussionmentioning

confidence: 92%

Fluorine-enhanced boron diffusion in germanium-preamorphized silicon

Jacques

Jones

Robertson

et al. 2005

Journal of Applied Physics

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Silicon wafers were preamorphized with 60 keV Ge + or 70 keV Si + at a dose of 1 ϫ 10 15 atoms/ cm 2. F + was then implanted into some samples at 6 keV at doses ranging from 1 ϫ 10 14 to 5 ϫ 10 15 atoms/ cm 2 , followed by 11 B + implants at 500 eV, 1 ϫ 10 15 atoms/ cm 2. Secondary-ion-mass spectrometry confirmed that fluorine enhances boron motion in germanium-preamorphized materials in the absence of annealing. The magnitude of boron diffusion scales with increasing fluorine dose. Boron motion in as-implanted samples occurs when fluorine is concentrated above 1 ϫ 10 20 atoms/ cm 3. Boron atoms are mobile in as-implanted, amorphous material at concentrations up to 1 ϫ 10 19 atoms/ cm 3. Fluorine directly influences boron motion only prior to activation annealing. During the solid-phase epitaxial regrowth process, fluorine does not directly influence boron motion, it simply alters the recrystallization rate of the silicon substrate. Boron atoms can diffuse in germanium-amorphized silicon during recrystallization at elevated temperatures without the assistance of additional dopants. Mobile boron concentrations up to 1 ϫ 10 20 atoms/ cm 3 are observed during annealing of germanium-preamorphized wafers.

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“…the integrated intensity of I x is proportional to exp(T/T 0 ) and best fit can be obtained for T 0 ¼ 117 K. This is qualitatively different from the thermal activation law, where the intensity increases proportional to exp(T 0 /T). Actually, it has long been observed that the temperature dependence of the intensity of PL in amorphous semiconductors obey the exp(ÀT/T 0 ) law [23]. Street et al [24] suggested that this kind of temperature dependence is related to the tunneling away of electron from the radiative recombination site to a trap.…”

Section: Photoluminescencementioning

confidence: 99%