Optical properties of thickness-controlled PtSe<sub>2</sub>thin films studied<i>via</i>spectroscopic ellipsometry

He, Junbo; Wei, Jian; Zhu, Xudan; Zhang, Rongjun; Wang, Jianlu; Zhu, Meiping; Wang, Song-You; Zheng, Yu‐Xiang; Chen, Liang‐Yao

doi:10.1039/d0cp04021e

Cited by 22 publications

(32 citation statements)

References 46 publications

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“…Then, the optical constants and absorption properties were investigated by the SE analysis and transmission spectra, as shown in Figure . As a noncontact and nondestructive technique, [ 38,39 ] SE has been extensively used in bulk materials, films, and even complex structures to explore their optical constants and dielectric properties. Two basic sets of data, psi ( ψ ) and delta (Δ), are collected in the measurements of Ga 2 O 3 thin films, which can be defined as follows [ 40 ]

ρ = r_{normalp} / r_{normals} = \tan (ψ) \exp (i Δ)

where r p and r s represent the complex ratios of Fresnel reflection coefficients for p‐ and s‐polarized light, respectively.…”

Section: Resultsmentioning

confidence: 99%

Atomic‐Layer‐Ti‐Doped Ga₂O₃ Thin Films with Tunable Optical Properties and Wide Ultraviolet Optoelectronic Responses

Liu

Zhu

et al. 2021

Physica Rapid Research Ltrs

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Doping and alloying in Ga2O3 to tune electronic and photonic behaviors is still urgent but challenging, whereas Ga2O3 has shown great promise in deep‐ultraviolet (DUV) photodetectors and functional high‐power devices. Herein, atomic‐layer‐Ti‐doped/incorporating Ga2O3 (TGO) thin films with tailored optical properties in the UV region from 200 to 400 nm are described. The Ti content in amorphous TGO thin films is controlled and adjusted up to 11 at% during a plasma‐enhanced atomic layer deposition (PE‐ALD) process. The composition‐dependent optical constants of both amorphous and polycrystalline TGO thin films are analyzed in the wavelength region of 200–800 nm through spectroscopic ellipsometry (SE) with a point‐by‐point fitting method. An obvious bandgap tuning effect and redshifted absorption edges are observed in the transmittance spectra of TGO thin films with increasing Ti concentration. Moreover, composition‐dependent optical constants and wide absorption are also verified by the significant and broadened DUV photoelectronic responses of TGO‐based photodetectors. It is believed that this work will help in understanding the DUV optical constants and bandgap transitions of TGO thin films used for functional optical devices in the UV region below 400 nm.

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ρ = r_{normalp} / r_{normals} = \tan (ψ) \exp (i Δ)

where r p and r s represent the complex ratios of Fresnel reflection coefficients for p‐ and s‐polarized light, respectively.…”

Section: Resultsmentioning

confidence: 99%

Atomic‐Layer‐Ti‐Doped Ga₂O₃ Thin Films with Tunable Optical Properties and Wide Ultraviolet Optoelectronic Responses

Liu

Zhu

et al. 2021

Physica Rapid Research Ltrs

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“…We also used Raman spectroscopy to confirm that the thickness dependence of the amplitude ratio of E g and A 1g modes agrees with previous studies (Figure S2, Supporting Information). [43,48] Structural characterizations are provided in Figure S3, Supporting Information.…”

Section: Steady-state Exciton Characteristicsmentioning

confidence: 99%

“…We attribute this absorption peak to the exciton resonance because the energy position agrees with both the calculated direct-gap exciton state (2.2 eV) [46] and also the exciton energy recently observed by ellipsometry in a 1L-thick PtSe 2 thin-film (2.18 eV). [48] To better understand the observed exciton resonance, we calculated the electronic band structure of 1L PtSe 2 using the G 0 W 0 approximation (see Experimental Section for details). The result is shown in Figure 1e, where the indirect band-gap marked by the green line is ≈2.53 eV, which is lower than the direct band-gap (solid black line; ≈2.8 eV).…”

Section: Steady-state Exciton Characteristicsmentioning

confidence: 99%

Exciton‐Dominated Ultrafast Optical Response in Atomically Thin PtSe₂

Bae

Nah

Lee

et al. 2021

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semiconducting systems. [1,2] A representative example is layered 2D semiconductors, where reduced dielectric screening leads to huge exciton binding energies up to several hundreds of meV, enabling strong excitonic light-matter interactions even at room temperature. Thus, excitons in 2D materials govern fundamental optical properties such as light absorption and emission. [3,4] Furthermore, excitons in 2D systems often couple with their unique physical properties, such as a thickness-dependent change in the bandgap nature and polarization-governed optical selection rules. These relationships provide rich physics and proper functionality for novel optoelectronic applications. [3][4][5] To fully exploit the excellent properties of excitons, it is essential to explore their behavior on ultrashort timescales. Many fundamental excitonic phenomena such as recombination, many-body interactions, and scattering mechanisms occur on femtosecond or picosecond timescales. [6][7][8][9][10][11][12][13] Also, ultrafast light-matter interactions can modulate excitons, enabling novel quantum memory and switching effects. [14][15][16][17][18][19] Therefore, understanding exciton behaviors on Strongly bound excitons are a characteristic hallmark of 2D semiconductors, enabling unique light-matter interactions and novel optical applications. Platinum diselenide (PtSe 2 ) is an emerging 2D material with outstanding optical and electrical properties and excellent air stability. Bulk PtSe 2 is a semimetal, but its atomically thin form shows a semiconducting phase with the appearance of a band-gap, making one expect strongly bound 2D excitons. However, the excitons in PtSe 2 have been barely studied, either experimentally or theoretically. Here, the authors directly observe and theoretically confirm excitons and their ultrafast dynamics in mono-, bi-, and tri-layer PtSe 2 single crystals. Steady-state optical microscopy reveals exciton absorption resonances and their thickness dependence, confirmed by first-principles calculations. Ultrafast transient absorption microscopy finds that the exciton dominates the transient broadband response, resulting from strong exciton bleaching and renormalized band-gap-induced exciton shifting. The overall transient spectrum redshifts with increasing thickness as the shrinking bandgap redshifts the exciton resonance. This study provides novel insights into exciton photophysics in platinum dichalcogenides.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202103400.

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“…[31] Nevertheless, we should note that the out-of-plane dielectric component of layerd materials such as MoS 2 can be extracted by thicker samples with substrates that can provide large interference enhancement such as the SiO 2 /Si substrate. [29] Moreover, to test whether there is any possible inplane anisotropy of the large-area single-crystalline MoS 2 monolayer, we adopt the generally accepted method [32] to rotate the azimuthal angle of the sample within 0 to 60 based on the hexagonal symmetry of 2H-MoS 2 and perform ellipsometry measurements. As shown in Figure S3, Supporting Information, there is no significant difference between the ellipsometric data collected at different azimuthal angles.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic Ellipsometry Investigation of Au‐Assisted Exfoliated Large‐Area Single‐Crystalline Monolayer MoS₂

Zou

Zhang

et al. 2021

Physica Rapid Research Ltrs

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The recent Au‐assisted mechanical exfoliation technique has enabled scalable fabrication of millimeter‐sized, high‐quality monolayer 2D crystals. Herein, spectroscopic ellipsometry characterization of as‐exfoliated single‐crystalline monolayer MoS2 is reported. By developing layer‐by‐layer ellipsometry measurements and analysis, the complex dielectric function of monolayer MoS2 is extracted. Compared with bulk MoS2, the A and B exciton peaks in the dielectric function spectrum nearly disappear in the 1L MoS2–Au hybrid system. The charge transfer at the 1L MoS2–Au interface is responsible for this observation and the conclusion is also supported by Raman, photoluminescence, and differential reflectance measurements. These results reveal the impact of the Au substrate on the dielectric response of 2D monolayers with strong excitonic effect and will deepen our understanding of the 1L MoS2–Au interaction.

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Optical properties of thickness-controlled PtSe₂thin films studiedviaspectroscopic ellipsometry

Abstract: Platinum diselenide (PtSe2) has attracted rich attention due to its intriguing physical properties for both fundamental research and promising applications in electronics and optoelectronics. Here, we explored the optical properties...

Cited by 22 publications

References 46 publications

Atomic‐Layer‐Ti‐Doped Ga₂O₃ Thin Films with Tunable Optical Properties and Wide Ultraviolet Optoelectronic Responses

Atomic‐Layer‐Ti‐Doped Ga₂O₃ Thin Films with Tunable Optical Properties and Wide Ultraviolet Optoelectronic Responses

Exciton‐Dominated Ultrafast Optical Response in Atomically Thin PtSe₂

Spectroscopic Ellipsometry Investigation of Au‐Assisted Exfoliated Large‐Area Single‐Crystalline Monolayer MoS₂

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Optical properties of thickness-controlled PtSe2thin films studiedviaspectroscopic ellipsometry

Abstract: Platinum diselenide (PtSe2) has attracted rich attention due to its intriguing physical properties for both fundamental research and promising applications in electronics and optoelectronics. Here, we explored the optical properties...

Cited by 22 publications

References 46 publications

Atomic‐Layer‐Ti‐Doped Ga2O3 Thin Films with Tunable Optical Properties and Wide Ultraviolet Optoelectronic Responses

Atomic‐Layer‐Ti‐Doped Ga2O3 Thin Films with Tunable Optical Properties and Wide Ultraviolet Optoelectronic Responses

Exciton‐Dominated Ultrafast Optical Response in Atomically Thin PtSe2

Spectroscopic Ellipsometry Investigation of Au‐Assisted Exfoliated Large‐Area Single‐Crystalline Monolayer MoS2

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Optical properties of thickness-controlled PtSe₂thin films studiedviaspectroscopic ellipsometry

Atomic‐Layer‐Ti‐Doped Ga₂O₃ Thin Films with Tunable Optical Properties and Wide Ultraviolet Optoelectronic Responses

Atomic‐Layer‐Ti‐Doped Ga₂O₃ Thin Films with Tunable Optical Properties and Wide Ultraviolet Optoelectronic Responses

Exciton‐Dominated Ultrafast Optical Response in Atomically Thin PtSe₂

Spectroscopic Ellipsometry Investigation of Au‐Assisted Exfoliated Large‐Area Single‐Crystalline Monolayer MoS₂