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Optical investigation of the natural electron doping in thin MoS2 films deposited on dielectric substrates.

Sercombe D, Schwarz S, Del Pozo-Zamudio O, Liu F, Robinson BJ, Chekhovich EA, Tartakovskii II, Kolosov O, Tartakovskii AI - Sci Rep (2013)

Bottom Line: However, large surface-to-volume ratio in thin films enhances the significance of surface interactions and charging effects requiring new understanding.PL spectra for MoS2 films deposited on SiO2 substrates are found to vary widely.Observed great sensitivity of optical characteristics of 2D films to surface interactions has important implications for optoelectronics applications of layered materials.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom.

ABSTRACT
Two-dimensional (2D) compounds provide unique building blocks for novel layered devices and hybrid photonic structures. However, large surface-to-volume ratio in thin films enhances the significance of surface interactions and charging effects requiring new understanding. Here we use micro-photoluminescence (PL) and ultrasonic force microscopy to explore the influence of the dielectric environment on optical properties of a few monolayer MoS2 films. PL spectra for MoS2 films deposited on SiO2 substrates are found to vary widely. This film-to-film variation is suppressed by additional capping of MoS2 with SiO2 and Si(x)N(y), improving mechanical coupling of MoS2 with surrounding dielectrics. We show that the observed PL non-uniformities are related to strong variation in the local electron charging of MoS2 films. In completely encapsulated films, negative charging is enhanced leading to uniform optical properties. Observed great sensitivity of optical characteristics of 2D films to surface interactions has important implications for optoelectronics applications of layered materials.

No MeSH data available.


(a–d) PL peak energies for A exciton complex in MoS2 thin films.Data for films deposited on thermally (PECVD) grown SiO2 substrates are shown in top (bottom) panels. Panels (a)–(b) and (c)–(d) show PL peak positions for uncapped and capped films, respectively.
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f3: (a–d) PL peak energies for A exciton complex in MoS2 thin films.Data for films deposited on thermally (PECVD) grown SiO2 substrates are shown in top (bottom) panels. Panels (a)–(b) and (c)–(d) show PL peak positions for uncapped and capped films, respectively.

Mentions: A statistical analysis of PL peak energies for films deposited on the two types of substrates is presented in Fig. 3. Fig. 3(a,b) show that the average values for the PL peak energies, , for uncapped films are for the PECVD substrates and for thermal oxide substrates, with an almost two times larger standard deviation, σEmax for the former (18 versus 11 meV). The data collected for the capped films (shaded for SixNy and hatched for SiO2) are presented in Fig. 3(c) and (d) for the thermal and PECVD oxide substrates, respectively. Significant narrowing of the peak energy distribution is found in all cases: σEmax ≈ 6 meV has been found. The average peak energies are very similar for both SiO2 and SixNy capping on the thermal oxide substrates (), but differ for PECVD substrates: and 1.870 eV for SiO2 and SixNy capping, respectively.


Optical investigation of the natural electron doping in thin MoS2 films deposited on dielectric substrates.

Sercombe D, Schwarz S, Del Pozo-Zamudio O, Liu F, Robinson BJ, Chekhovich EA, Tartakovskii II, Kolosov O, Tartakovskii AI - Sci Rep (2013)

(a–d) PL peak energies for A exciton complex in MoS2 thin films.Data for films deposited on thermally (PECVD) grown SiO2 substrates are shown in top (bottom) panels. Panels (a)–(b) and (c)–(d) show PL peak positions for uncapped and capped films, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3860010&req=5

f3: (a–d) PL peak energies for A exciton complex in MoS2 thin films.Data for films deposited on thermally (PECVD) grown SiO2 substrates are shown in top (bottom) panels. Panels (a)–(b) and (c)–(d) show PL peak positions for uncapped and capped films, respectively.
Mentions: A statistical analysis of PL peak energies for films deposited on the two types of substrates is presented in Fig. 3. Fig. 3(a,b) show that the average values for the PL peak energies, , for uncapped films are for the PECVD substrates and for thermal oxide substrates, with an almost two times larger standard deviation, σEmax for the former (18 versus 11 meV). The data collected for the capped films (shaded for SixNy and hatched for SiO2) are presented in Fig. 3(c) and (d) for the thermal and PECVD oxide substrates, respectively. Significant narrowing of the peak energy distribution is found in all cases: σEmax ≈ 6 meV has been found. The average peak energies are very similar for both SiO2 and SixNy capping on the thermal oxide substrates (), but differ for PECVD substrates: and 1.870 eV for SiO2 and SixNy capping, respectively.

Bottom Line: However, large surface-to-volume ratio in thin films enhances the significance of surface interactions and charging effects requiring new understanding.PL spectra for MoS2 films deposited on SiO2 substrates are found to vary widely.Observed great sensitivity of optical characteristics of 2D films to surface interactions has important implications for optoelectronics applications of layered materials.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom.

ABSTRACT
Two-dimensional (2D) compounds provide unique building blocks for novel layered devices and hybrid photonic structures. However, large surface-to-volume ratio in thin films enhances the significance of surface interactions and charging effects requiring new understanding. Here we use micro-photoluminescence (PL) and ultrasonic force microscopy to explore the influence of the dielectric environment on optical properties of a few monolayer MoS2 films. PL spectra for MoS2 films deposited on SiO2 substrates are found to vary widely. This film-to-film variation is suppressed by additional capping of MoS2 with SiO2 and Si(x)N(y), improving mechanical coupling of MoS2 with surrounding dielectrics. We show that the observed PL non-uniformities are related to strong variation in the local electron charging of MoS2 films. In completely encapsulated films, negative charging is enhanced leading to uniform optical properties. Observed great sensitivity of optical characteristics of 2D films to surface interactions has important implications for optoelectronics applications of layered materials.

No MeSH data available.