Modeling the transport properties of epitaxially grown thermoelectric oxide thin films using spectroscopic ellipsometry

Kumar, S. R. Sarath; Abutaha, Anas; Hedhili, Mohamed N.; Alshareef, Husam N.

doi:10.1063/1.3678186

Cited by 8 publications

(4 citation statements)

References 28 publications

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“…SrTiO 3 is a typical perovskite-structured oxide with a large bandgap of 3.2 eV [7,8,9], which can have its chemical and electrical properties tuned either by doping or by controlling the number of oxygen vacancies [10,11]. It is well known that the properties of SrTiO 3 nanoparticles strongly depend on their morphology, structure, chemical composition, and crystallinity [12,13].…”

Section: Introductionmentioning

confidence: 99%

Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

et al. 2015

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To provide a convenient and practical synthesis process for metal ion doping on the surface of nanoparticles in an assembled nanostructure, core-shell-structured La-doped SrTiO3 nanocubes with a Nb-doped surface layer were synthesized via a rapid synthesis combining a rapid sol-precipitation and hydrothermal process. The La-doped SrTiO3 nanocubes were formed at room temperature by a rapid dissolution of NaOH pellets during the rapid sol-precipitation process, and the Nb-doped surface (shell) along with Nb-rich edges formed on the core nanocubes via the hydrothermal process. The formation mechanism of the core-shell-structured nanocubes and their shape evolution as a function of the Nb doping level were investigated. The synthesized core-shell-structured nanocubes could be arranged face-to-face on a SiO2/Si substrate by a slow evaporation process, and this nanostructured 10 μm thick thin film showed a smooth surface.

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Section: Introductionmentioning

confidence: 99%

Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

et al. 2015

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“…Undoped bulk STO is an insulator at room temperature with a large band gap of ~3.2 eV, due to its closed shell d 0 electron configuration . Insulating STO can be transformed into a semiconductor or conductor by creating defect levels close to the conduction or valence bands, for example, by doping either the Sr 2+ sites with La or Ho ions, Ti 4+ sites with Nb or In ions, etc., or by forming oxygen vacancies . The donor‐doped STO ( n ‐type) has been intensively studied for a long time, whereas the acceptor‐doped STO ( p ‐type) is seldom reported.…”

Section: Introductionmentioning

confidence: 99%

Electrical and Optical Properties of Transparent Conducting p‐Type SrTiO₃ Thin Films

Huang

Nechache

et al. 2015

J. Am. Ceram. Soc.

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We report a systematic study of the electrical and optical properties of epitaxial perovskite p‐type In‐doped SrTiO3 thin films (SrInxTi1−xO3, 0 ≤ x ≤ 0.15) grown on single‐crystal (100)‐oriented LaAlO3 substrates using a hybrid method which combines pulsed laser deposition and molecular beam epitaxy in a range of deposition conditions. X‐ray diffraction analysis confirms the epitaxial growth of high crystal quality films. Four‐point probe and Hall Effect measurements demonstrate that the films are p‐type semiconductors with a low resistivity of ~10−2 Ω·cm and a high carrier concentration of ~1019 cm−3. The optical transmittance spectra reveal that the films are highly transparent (˃70%) in the visible region.

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“…In this work, SE is adopted to determine m Ã e , which avoids the inaccuracies resulted from theoretical approximations. The combination of the Drude model and Lorentz model is employed in SE analysis, and the complex dielectric function can be given by 20,21 …”

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Stress-induced anomalous shift of optical band gap in Ga-doped ZnO thin films: Experimental and first-principles study

Wang

Tang

Liu

et al. 2015

Applied Physics Letters

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In this work, highly c-axis oriented Ga-doped ZnO thin films have been deposited on glass substrates by RF magnetron sputtering under different sputtering times. The optical band gap is observed to shift linearly with the electron concentration and in-plane stress. The failure of fitting the shift of band gap as a function of electron concentration using the available theoretical models suggests the in-plane stress, instead of the electron concentration, be regarded as the dominant cause to this anomalous redshift of the optical band gap. And the mechanism of stress-dependent optical band gap is supported by the first-principles calculation based on density functional theory. V C 2015 AIP Publishing LLC. [http://dx.Zinc oxide (ZnO) is a wide band gap semiconductor with a large exciton binding energy at room temperature. Recently, doped ZnO thin film has attracted great attention because of its application as transparent electrodes for flat panel displays and photovoltaic cells, 1,2 which motivates us to extensively study the optical properties of doped ZnO films, such as plasma frequency and optical band gap.Generally, the optical band gap of doped transparent conductive oxide (TCO) films can be larger or smaller than that of the undoped films. Most of the studies attribute the shift of band gap to two competing effects: the BursteinMoss (BM) effect 3,4 from partial filling of the states at the bottom of the conduction band and the band gap renormalization (BGR) effect 5 due to different many-body interactions. However, other effects, like strain, can also affect the optical band gap of films significantly. If only the carrier concentration is taken into consideration, it could lead to an inaccurate analysis on the change of optical band gap, as presented in many previous studies. 6,7 Since stress occurs inevitably due to the defects and impurities in the films and leads to the changes in the electrical and optical properties of the thin films, "stress engineering" has been widely employed in the design of electronic devices to modulate the optical band gap by introducing some impurities. Despite the significance to understand the effect of stress on the band gap, there are few reports on first-principles theoretical study of Ga-doped ZnO (GZO) thin films to illuminate the effect of stress on the electronic structures. Nevertheless, this work presents a systematical study of the optical band gap shift in GZO thin films based on the combination of experimental study and first-principles calculation.GZO thin films were deposited on glass substrates by RF magnetron sputtering using a GZO ceramic target (Ga 2 O 3 : ZnO ¼ 3:97 wt. %, U 55 Â 5 mm, purity of 99.99%) for a deposition time from 15 to 45 min, in steps of 10 min.The distance between the substrate and the target was kept to be 60 mm. The GZO film samples were deposited in the vacuum chamber under a pressure of 7.5 Â 10 À4 Pa, followed by the introduction of 99.99% pure argon at a flow rate of 150 sccm. The sputtering was carried out under a pressure of 1.5 P...

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Modeling the transport properties of epitaxially grown thermoelectric oxide thin films using spectroscopic ellipsometry

Cited by 8 publications

References 28 publications

Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

Electrical and Optical Properties of Transparent Conducting p‐Type SrTiO₃ Thin Films

Stress-induced anomalous shift of optical band gap in Ga-doped ZnO thin films: Experimental and first-principles study

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Modeling the transport properties of epitaxially grown thermoelectric oxide thin films using spectroscopic ellipsometry

Cited by 8 publications

References 28 publications

Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

Electrical and Optical Properties of Transparent Conducting p‐Type SrTiO3 Thin Films

Stress-induced anomalous shift of optical band gap in Ga-doped ZnO thin films: Experimental and first-principles study

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Electrical and Optical Properties of Transparent Conducting p‐Type SrTiO₃ Thin Films