Durability and photo-electric characteristics of a mille-feuille structured amorphous selenium (a-Se)–arsenic selenide (As2Se3) multi-layered thin film

Saito, Ichitaro; Masuzawa, Tomoaki; Kudo, Yoshihisa; Pittner, Steve; Yamada, Takatoshi; Koh, Angel T. T.; Chua, Daniel H. C.; Mori, Yusuke; Zahn, Dietrich R. T.; Amaratunga, G.A.J.; Okano, Ken

doi:10.1016/j.jnoncrysol.2013.06.022

Cited by 8 publications

(7 citation statements)

References 9 publications

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“…A 200 nm superlattice‐Se sample was used for the TOF‐SIMS and the results are shown in Figure . The details of the fabrication and TOF‐SIMS are found in literature . From the TOF‐SIMS result, it is possible to estimate the thickness of each superlattice layer.…”

Section: Experiments and Resultsmentioning

confidence: 99%

“…The FWHM gave values of thickness from 6 to 9 nm. These values agree with estimates made from the rotational speed and duration of deposition, and with measurements from previous work . The result confirms that across the deposition thickness, there are alternating layers of Se and As 2 Se 3 with a period of 12–18 nm.…”

Section: Experiments and Resultsmentioning

confidence: 99%

“…With the exception of cascade multiplication, most models treat the amorphous Se as a bulk material in which As 2 Se 3 is only incorporated to stabilize the material against thermal degradation. A bulk material of the same stoichiometry as the Se and As 2 Se 3 layered structure does not exhibit photomultiplication . However, cascade multiplication hints that the layered structure creates separate regions for acceleration and for collision.…”

Section: Introductionmentioning

confidence: 99%

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Transport Properties of Se/As₂Se₃ Nanolayer Superlattice Fabricated Using Rotational Evaporation

John

Okano

Sharma

et al. 2019

Adv Funct Materials

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Since their proposal by Esaki, superlattices have been observed to have fascinating features such as quantum size effects, negative differential resistance, and sequential resonant tunneling. However, the technology threshold for fabricating superlattices is high, requiring methods like molecular beam epitaxy (MBE) and atomic layer deposition (ALD), among others, even for amorphous materials. Thus, the desirable features from superlattices have not been extensively utilized. It is shown that superlattices of Se and As2Se3 (superlattice‐Se), fabricated using rotational evaporation, exhibit sequential tunneling, a typical superlattice feature. From current–voltage measurements of the superlattice deposited on n‐type Si, oscillations in the characteristics are observed. Using models of reverse‐biased Schottky barriers, the observations are explained as tunneling in sequence from superlattice minibands. The superlattice‐Se also shows carrier blocking, with a resistivity of the order of 1012 Ω cm in dark conditions at room temperature, despite the low resistivity (≈10 Ω cm) of the n‐type Si substrate. When the Si is illuminated, the device shows higher detectivity for weaker signals compared to higher illumination. The ease of fabrication, and the blocking and amplifying capabilities make superlattice‐Se an interesting “add‐on” structure to improve conventional photodetector materials such as Si or Ge, which have issues with dark currents at room temperature.

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Section: Experiments and Resultsmentioning

confidence: 99%

Section: Experiments and Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Transport Properties of Se/As₂Se₃ Nanolayer Superlattice Fabricated Using Rotational Evaporation

John

Okano

Sharma

et al. 2019

Adv Funct Materials

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“…At a measured thickness of 2 µm the rotational evaporation was stopped and the samples extracted. Details of the fabrication and characterization of this Se based multilayer film (hereafter referred to as multi‐Se) are found in literature …”

Section: Methodsmentioning

confidence: 99%

Modifying the Electronic Properties of Se/n‐Si Heterostructure Using Electrolysis

John

Enomoto

Miyachi

et al. 2018

Physica Status Solidi (b)

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Heterostructures of dissimilar crystalline materials are key in the development of photoelectronic devices. Such structures rely on matching lattice constants for efficient transport. Nevertheless, an amorphous material, amorphous Se is becoming important in high‐energy photoelectronics. Thus there is a need to understand the heterostructures it forms with conventional crystalline materials. Since the transport properties of such heterostructures will be limited by lattice mismatches, methods to improve transport are necessary. We investigated the effect of electrolysis on the electronic properties of Se based multilayer films deposited on n‐type silicon (Se/n‐Si) and showed that conduction and photoresponse can be changed by electrolysis processing. The Se surface of the Se/n‐Si samples was used as an anode in the electrolysis of NaCl solution. Afterwards, the samples were measured using current–voltage and capacitance–voltage variations in dark conditions and under illumination. Electrolysis processed samples showed higher conduction current and photocurrent, compared to samples not used in electrolysis. This is due to the introduction of Cl into the Se, which affects carrier lifetimes: increasing hole lifetime and reducing electron lifetime. We therefore suggest that electrolysis can be applied to modify the electronic properties of Se/n‐Si heterostructures.

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“…Using the rotational evaporation technique, samples of the individual materials, namely amorphous Se only, As 2 Se 3 only, and the multi-layer combination of the two materials, were fabricated [17]. The substrates were n-type Si (100), 5-8 Ω cm, single side polished wafers diced into 10 mm squares.…”

Section: Fabricationmentioning

confidence: 99%

Spectroscopic ellipsometry of amorphous Se superlattices

John¹,

Okano²,

Sharma³

et al. 2021

J. Phys. D: Appl. Phys.

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Superlattice structures have a variety of electrical and optical properties that allow for interesting applications like quantum cascade lasers and ultrasensitive photo-detectors. However, such structures require high-tech fabrication methods like molecular beam epitaxy, and this technology barrier means that these promising devices are not in widespread use. Using the simple method of rotational evaporation, we fabricated films with alternating multi-nanolayers of amorphous selenium (Se) and arsenic selenide (As2Se3). We investigated the optical properties of the individual materials, and the resulting multi-layer structure using spectroscopic ellipsometry. The results were modeled using Cody–Lorentz oscillators to obtain the refractive index (n) and extinction coefficient (k). The models showed the optical band gaps of Se and As2Se3 to be 1.97 and 1.69 eV, respectively. The absorption coefficient (α) of the multi-layer structure showed a series of five ‘steps’ in energy at 1.72, 1.82, 1.89, 1.97, and 2.04 eV. These are confirmed to stem from the transitions between confined quantum well levels due to the superlattice structure. In this way, the optical measurement using spectroscopic ellipsometry confirms the possibility of fabricating good quality nanostructutres using amorphous materials and rotational evaporation.

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Durability and photo-electric characteristics of a mille-feuille structured amorphous selenium (a-Se)–arsenic selenide (As2Se3) multi-layered thin film

Cited by 8 publications

References 9 publications

Transport Properties of Se/As₂Se₃ Nanolayer Superlattice Fabricated Using Rotational Evaporation

Transport Properties of Se/As₂Se₃ Nanolayer Superlattice Fabricated Using Rotational Evaporation

Modifying the Electronic Properties of Se/n‐Si Heterostructure Using Electrolysis

Spectroscopic ellipsometry of amorphous Se superlattices

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Durability and photo-electric characteristics of a mille-feuille structured amorphous selenium (a-Se)–arsenic selenide (As2Se3) multi-layered thin film

Cited by 8 publications

References 9 publications

Transport Properties of Se/As2Se3 Nanolayer Superlattice Fabricated Using Rotational Evaporation

Transport Properties of Se/As2Se3 Nanolayer Superlattice Fabricated Using Rotational Evaporation

Modifying the Electronic Properties of Se/n‐Si Heterostructure Using Electrolysis

Spectroscopic ellipsometry of amorphous Se superlattices

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Product

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Transport Properties of Se/As₂Se₃ Nanolayer Superlattice Fabricated Using Rotational Evaporation

Transport Properties of Se/As₂Se₃ Nanolayer Superlattice Fabricated Using Rotational Evaporation