Thickness effect on the band gap and optical properties of germanium thin films

Goh, Eunice S. M.; Chen, T. P.; Sun, Chang Q.; Liu, Y. C.

doi:10.1063/1.3291103

Cited by 129 publications

(48 citation statements)

References 23 publications

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“…10 illustrates that refractive indices increase with increasing thickness. Such refractive index increases with increasing thickness for Zn 0.995 Ni 0.005 S nanocrystalline thin film is in good agreement with thickness effect reported for other materials [32,33].…”

Section: Refractive Index Dispersion Of Zn 1−x Ni X S Nanocrystallinesupporting

confidence: 91%

Structural and optical investigation of nanocrystalline Zn1−xNixS diluted magnetic semiconductor thin films

Emam-Ismail

El-Hagary

Shaaban

et al. 2012

Journal of Alloys and Compounds

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Section: Refractive Index Dispersion Of Zn 1−x Ni X S Nanocrystallinesupporting

confidence: 91%

Structural and optical investigation of nanocrystalline Zn1−xNixS diluted magnetic semiconductor thin films

Emam-Ismail

El-Hagary

Shaaban

et al. 2012

Journal of Alloys and Compounds

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“…Further, the data presented in Table 2 confirmed that the optical band gap decreased with the increase in VO-MO film thickness. These observations could be explained in terms of the well recognized quantum confinement or size effect354354.…”

Section: Resultsmentioning

confidence: 92%

Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties

Dey

Nayak

Akinlabi

et al. 2016

Sci Rep

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Vanadium oxide-molybdenum oxide (VO-MO) thin (21-475 nm) films were grown on quartz and silicon substrates by pulsed RF magnetron sputtering technique by altering the RF power from 100 to 600 W. Crystalline VO-MO thin films showed the mixed phases of vanadium oxides e.g., V 2 O 5 , V 2 O 3 and VO 2 along with MoO 3 . Reversible or smart transition was found to occur just above the room temperature i.e., at ~45-50 °C. The VO-MO films deposited on quartz showed a gradual decrease in transmittance with increase in film thickness. But, the VO-MO films on silicon exhibited reflectance that was significantly lower than that of the substrate. Further, the effect of low temperature (i.e., 100 °C) vacuum (10 −5 mbar) annealing on optical properties e.g., solar absorptance, transmittance and reflectance as well as the optical constants e.g., optical band gap, refractive index and extinction coefficient were studied. Sheet resistance, oxidation state and nanomechanical properties e.g., nanohardness and elastic modulus of the VO-MO thin films were also investigated in as-deposited condition as well as after the vacuum annealing treatment. Finally, the combination of the nanoindentation technique and the finite element modeling (FEM) was employed to investigate yield stress and von Mises stress distribution of the VO-MO thin films.Vanadium oxides based films and coatings are extensively studied due to both thermochromic 14,15,[17][18][19][20]24,25,31 . The Mo and/or molybdenum oxide doped vanadium oxides are reported to be grown by a multitude of techniques such as magnetron sputtering technique 15 , atmospheric pressure chemical vapour deposition 26 , cathodic

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“…It has been reported that when the thickness of ZnO and Ge thin films scales down to 20 nm, the ultrathin films exhibit an expansion of bandgap and a reduction of dielectric function due to the quantum confinement effect. 10,13 As shown in Fig. 2a for the IGZO thin films thinner than ∼20 nm, the ultrathin films exhibit a blueshift in both real and imaginary parts of dielectric function with decreasing film thickness.…”

Section: Ellipsometric Modelingmentioning

confidence: 89%

“…It has been shown that thickness dependence of band gaps of ultrathin amorphous materials can be described by the ODQC effect. 13,16 Figure 4 shows the bandgap energy of the IGZO thin films yielded from the SE modelling. A significant dependence of bandgap on film thickness is observed.…”

Section: Ellipsometric Modelingmentioning

confidence: 99%

Thickness Dependence of Optical Properties of Amorphous Indium Gallium Zinc Oxide Thin Films: Effects of Free-Electrons and Quantum Confinement

Chen

et al. 2015

ECS Solid State Letters

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Dielectric function of amorphous indium gallium zinc oxide (a-IGZO) thin films is found to shift significantly with the film thickness, which is attributed to the changes in both the bandgap and electron concentration of the IGZO thin films with the film thickness. The ultrathin films (film thickness < ∼20 nm) exhibit a bandgap expansion with reducing film thickness due to the quantum confinement effect; while the thicker films (thickness > ∼35 nm) demonstrate the free-electron effect, i.e. the Burstein-Moss shift and increase of free-electrons absorption with increasing electron concentration Amorphous indium gallium zinc oxide (a-IGZO) is a transparent semiconductor material that has promising application in next generation flat panel display due to its high electron mobility and high transparency in visible. 1,2 Although intensive electrical studies have been carried out on the IGZO thin films, 3-6 there is still lack of detailed optical study of the complex dielectric function, one of the fundamental optical properties, of the IGZO thin films. It has been shown in our early work that free-electron concentration of a metal oxide thin film could have a significant impact on the optical properties of the oxide film, in particular, the onset absorption near the band edge. 7 When the electron concentration reaches ∼10 18 -10 19 cm −3 , a semiconductor-to-metal transition occurs, and the conduction band of the oxide semiconductor is partially filled with free electrons, resulting in a bandgap expansion as a result of the Burstein-Moss effect. 8 The dependence of carrier concentration on film thickness could further complicate the situation. 9 On the hand, it has also been shown that when a crystalline oxide film scales down to the nanoscale regime (e.g., the film thickness is less than ∼20 nm), the nanoscale structures exhibit some unique properties different from their bulk counterparts due to quantum confinement effect. 10 Therefore, it is interesting to study the thickness-dependence of the complex dielectric function of a-IGZO thin films as both the free-electron and quantum confinement effects on the optical properties of the oxide films are dependent of the film thickness.In this work, we present a study of the evolution of optical properties of a-IGZO thin films with film thickness. The bandgap and complex dielectric function of the IGZO thin films with various film thicknesses have been determined with spectroscopic ellipsometry (SE) based on the Tauc-Lorentz-Drude (TL-Drude) model. 8 It is observed that the complex dielectric function is strongly dependent of the film thickness. The ultrathin films (thickness < ∼20 nm) show a blueshift of both the real and imaginary parts of the complex dielectric function and an expansion of bandgap with decreasing film thickness due to the quantum confinement effect; in contrast, the thicker films (thickness > ∼35 nm) exhibit both the Burstein-Moss shift and enhancement of free-electrons absorption with increasing film thickness, which are related to the increase of elec...

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Thickness effect on the band gap and optical properties of germanium thin films

Cited by 129 publications

References 23 publications

Structural and optical investigation of nanocrystalline Zn1−xNixS diluted magnetic semiconductor thin films

Structural and optical investigation of nanocrystalline Zn1−xNixS diluted magnetic semiconductor thin films

Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties

Thickness Dependence of Optical Properties of Amorphous Indium Gallium Zinc Oxide Thin Films: Effects of Free-Electrons and Quantum Confinement

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