Composition dependent properties of p- and n-type polycrystalline group-IV alloy thin films

Mizoguchi, Takuto; Imajo, Toshifumi; Sekiguchi, Takashi; Suemasu, Takashi; Toko, Kaoru

doi:10.1016/j.jallcom.2021.161306

Cited by 10 publications

(13 citation statements)

References 62 publications

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“…Figure 3a shows that σ is slightly higher for p-type SiGe than for n-type SiGe, despite n-type SiGe having a higher carrier concentration. This is because p-type SiGe has a higher carrier mobility, which likely can be attributed to several features including higher Ge concentration [40], larger grain size (see Figure 2b), thicker film (hence less interfacial carrier scattering) [41], and lower grain boundary potential than for n-type SiGe [42,43]. For both samples, the σ values are slightly lower than those of the quartz glass substrate samples [35,36], which is consistent with the grain size trend shown in Figure 2b.…”

Section: Resultsmentioning

confidence: 99%

Flexible Thermoelectric Generator Based on Polycrystalline SiGe Thin Films

Ozawa

Murata²,

Suemasu

et al. 2022

Materials

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Flexible and reliable thermoelectric generators (TEGs) will be essential for future energy harvesting sensors. In this study, we synthesized p- and n-type SiGe layers on a high heat-resistant polyimide film using metal-induced layer exchange (LE) and demonstrated TEG operation. Despite the low process temperature (<500 °C), the polycrystalline SiGe layers showed high power factors of 560 µW m−1 K−2 for p-type Si0.4Ge0.6 and 390 µW m−1 K−2 for n-type Si0.85Ge0.15, owing to self-organized doping in LE. Furthermore, the power factors indicated stable behavior with changing measurement temperature, an advantage of SiGe as an inorganic material. An in-plane π-type TEG based on these SiGe layers showed an output power of 0.45 µW cm−2 at near room temperature for a 30 K temperature gradient. This achievement will enable the development of environmentally friendly and highly reliable flexible TEGs for operating micro-energy devices in the future Internet of Things.

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Section: Resultsmentioning

confidence: 99%

Flexible Thermoelectric Generator Based on Polycrystalline SiGe Thin Films

Ozawa

Murata²,

Suemasu

et al. 2022

Materials

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“…39,40 This behavior is due to the densification effects of the amorphous precursor in SPC. 35,41,42 The grain size decreases at high x (>0.1), likely because the deposition temperature of 150 °C is low for densifying the Ge 1−x Si x precursor. 42 Conversely, with increasing y, the grain size increases and subsequently decreases.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…35,42 The samples were loaded into a conventional tube furnace in a N 2 atmosphere and annealed to induce SPC at a T SPC of 450−500 °C for 5 h (Table 1); T SPC was determined based on the crystallization rate of Ge 1−x−y Si x Sn y of each composition. 42 SOG with Ga and P dopants was coated on the surface of polycrystalline Ge 1−x−y Si x Sn y layers and then hardened by annealing at 200 °C for 30 min. Subsequently, the samples were annealed at a T DA of 550−750 °C for 10 h for P and 750−800 °C for 30 min for Ga in an Ar atmosphere to diffuse and activate dopant impurities in Ge 1−x−y Si x Sn y (Table 1); T DA was determined based on the diffusion rate of impurities in Ge and Si.…”

Section: ■ Conclusionmentioning

confidence: 99%

High Thermoelectric Performance in Polycrystalline GeSiSn Ternary Alloy Thin Films

Maeda

Ishiyama

Nishida

et al. 2022

ACS Appl. Mater. Interfaces

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Group IV materials are promising candidates for highly reliable and human-friendly thin-film thermoelectric generators, used for micro-energy harvesting. In this study, we investigated the synthesis and thermoelectric applications of a Ge-based ternary alloy thin film, Ge1–x–y Si x Sn y . The solid-phase crystallization of the highly densified amorphous precursors allowed the formation of high-quality polycrystalline Ge1–x–y Si x Sn y layers on an insulating substrate. The small compositions of Si and Sn in Ge1–x–y Si x Sn y (x < 0.15 and y < 0.05) lowered the thermal conductivity (3.1 W m–1 K–1) owing to the alloy scattering of phonons, while maintaining a high carrier mobility (approximately 200 cm2 V–1 s–1). The solid-phase diffusion of Ga and P allowed us to control the carrier concentration to the order of 1019 cm–3 for holes and 1018 cm–3 for electrons. For both p- and n-type Ge1–x–y Si x Sn y , the power factor peaked at x = 0.06 and y = 0.02, reaching 1160 μW m–1 K–2 for p-type and 2040 μW m–1 K–2 for n-type. The resulting dimensionless figure of merits (0.12 for p-type and 0.20 for n-type) are higher than those of most environmentally friendly thermoelectric thin films. These results indicate that group IV alloys are promising candidates for high-performance, reliable thin-film thermoelectric generators.

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“…The conductivity of polycrystalline silicon is significantly influenced by the potential barrier, since the effective mobility of carriers is figured out by the potential barrier, as shown in Equations (1) and (2) [ 11 , 12 , 13 , 14 , 15 , 16 ].

…”

Section: Discussionmentioning

confidence: 99%

Electron Radiation Effects of Grain-Boundary Evolution on Polycrystalline Silicon in MEMS

2022

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A specimen observed with a transmission electron microscope (TEM) was processed by focused ion beam (FIB) from a surface-micromachined polycrystalline silicon MEMS structure. Electron irradiation and in situ observation were performed on a selected grain boundary in the specimen. The grain boundary was observed and located by using lattice-oriented selective TEM photography. An evolution progress of amorphization of small silicon grain within the grain boundary and recrystallization of amorphous silicon were observed. A silicon grain turned into several smaller bar grains within the grain boundary. The mechanism of grain-boundary evolution inducing a change of conductivity of polycrystalline silicon has been revealed. The conductivity of polycrystalline silicon influenced by electron irradiation could be attributed to the change of grain boundary.

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Composition dependent properties of p- and n-type polycrystalline group-IV alloy thin films

Cited by 10 publications

References 62 publications

Flexible Thermoelectric Generator Based on Polycrystalline SiGe Thin Films

Flexible Thermoelectric Generator Based on Polycrystalline SiGe Thin Films

High Thermoelectric Performance in Polycrystalline GeSiSn Ternary Alloy Thin Films

Electron Radiation Effects of Grain-Boundary Evolution on Polycrystalline Silicon in MEMS

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