Nanostructured multilayer TiO2–Ge films with quantum confinement effects for photovoltaic applications

Khan, Abdul Faheem; Mehmood, Mazhar; Aslam, Muhammad; Shah, S. İsmat

doi:10.1016/j.jcis.2009.11.045

Cited by 33 publications

(13 citation statements)

References 22 publications

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“…This implies that even though peak positions in these samples are characteristic to crystalline rutile formation there is no long range ordering in these samples and the Raman shifts are most likely represented by amorphous vibrations. It has been suggested that peak broadening occurs due to nanocrystallinity and quantum confinement effects, and that there is a characteristic dependency between grain size and peak position and broadening in Raman analysis [23,[25][26][27]. Finally Li Bassi et al [22] pointed out that materials with smaller particles (~4.4 nm) have Raman spectrum similar to that of amorphous materials, which could also be the case here.…”

Section: Resultssupporting

confidence: 55%

“…Within this representation 1A 1g , 2B 1g , 3E g are Raman active, whereas the remaining modes are active in Infrared [24]. Raman analysis gives information about the nature of the bonds in a structure and there is substantial evidence indicating that the peak position, shape and intensity of Raman peaks are related to sub-stoichiometric defects, quantum confinement effects, crystal sizes, nanocrystallinity and large interfacial areas [22,23,25,26]. Spectra obtained from the titania films produced in this work were compared against those obtained for pure titania nano-crystals to allow any variations in phase, stoichiometry or degree of crystallisation in the analysed films to be identified.…”

Section: Resultsmentioning

confidence: 99%

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Characterisation Studies of the Structure and Properties of As-Deposited and Annealed Pulsed Magnetron Sputtered Titania Coatings

et al. 2013

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Titanium dioxide thin films are durable, chemically stable, have a high refractive index and good electro/photochemical proprieties. Consequently, they are widely used as anti-reflective layers in optical devices and large area glazing products, dielectric layers in microelectronic devices and photo catalytic layers in self-cleaning surfaces. Titania coatings may have amorphous or crystalline structures, where three crystalline phases of TiO 2 can be obtained: anatase, rutile and brookite, although the latter is rarely found. It is known, however, that the structure of TiO 2 coatings is sensitive to deposition conditions and can also be modified by post-deposition heat treatments. In this study, titania coatings have been deposited onto soda-lime glass substrates by reactive sputtering from a metallic target. The magnetron was driven in mid-frequency pulsed DC mode. The as-deposited coatings were analysed by micro Raman spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Selected coatings were annealed at temperatures in the OPEN ACCESSCoatings 2013, 3 167 range 200-700 °C and re-analysed. Whilst there was weak evidence of a nanocrystallinity in the as-deposited films, it was observed that these largely amorphous low temperature structures converted into strongly crystalline structures at annealing temperatures above 400 °C.

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Section: Resultssupporting

confidence: 55%

Section: Resultsmentioning

confidence: 99%

Characterisation Studies of the Structure and Properties of As-Deposited and Annealed Pulsed Magnetron Sputtered Titania Coatings

et al. 2013

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“…Similarly, several groups experimentally observed the size effect of bandgap enhancement in TiO 2 nanocrystals and reported a considerable increase in the bandgap to beyond 3.1 eV, which is suitable for TSO-related applications [246][247][248][249]. Several groups observed this quantum size effect in multilayer/heterojunction/nanocomposite TiO 2 /Ge and TiO 2 / ZnO films with interesting photovoltaic/photoconductive applications [250][251][252].…”

Section: Electro-optical Propertiesmentioning

confidence: 97%

Recent developments in TiO2 as n- and p-type transparent semiconductors: synthesis, modification, properties, and energy-related applications

2015

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TiO 2 -based thin films and nanomaterials have been fabricated via physical and solution-based techniques by various research groups around the globe. Generally, most applications of TiO 2 involve photocatalytic activity for water and air purification, self-cleaning surfaces, antibacterial activity, and superhydrophilicity. As a widebandgap semiconductor, modified TiO 2 belongs to a class of materials called transparent semiconducting oxides (TSOs), which are simultaneously optically transparent and electrically conductive. TSOs continue to be in high demand for a variety of applications ranging from transparent electronics and sensor devices to light detecting and emitting devices in telecommunications. However, reports on TiO 2 applications as an effective TSO for transparent electronics applications have been limited. In general, TiO 2 is intrinsically an n-type semiconductor but can be doped to have p-type semiconductivity. This provides a very important opportunity to fabricate all-transparent homojunction devices for light harvesting and energy storage. P-type TSOs have recently attracted tremendous interest in the field of active devices for emerging transparent electronics for potential use in ultra-violet light-based solar cells. Therefore, a detailed overview of the synthesis, band structure modification via doping, properties, and applications of modified TiO 2 as n-and p-type TSOs is warranted. This article comprehensively reviews the latest developments. The discussion includes solution-based wet chemical techniques and vacuum-based dry physical techniques fabricating TiO 2 -TSOs. The synthesis of p-TiO 2 in particular is discussed in detail as it may provide interesting breakthroughs in emerging transparent electronics applications. Also, the structural, optical, and electrical properties of TiO 2 are discussed in the context of TSO applications, specifically the defect chemistry of TiO 2 to obtain n-and p-type semiconductivity, which could provide interesting insights into the band structure engineering of TiO 2 for conductivity reversal. Applications of both nand p-type TiO 2 have been reviewed in detail in relation to thin film transparent homo/heterojunction devices, dyesensitized solar cells, electrochromic displays, and other energy-related applications.

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“…Impedance spectroscopy is a powerful technique to characterize intrinsic electrical properties of a material or film. The basis of EIS is the analysis of the impedance of the system under investigation based on the applied frequency, current and voltage [41]. The complex impedance is expressed as: Z (w) = Z ′(w) − iZ″(w), where Z′ is the real part and Z″ is the imaginary part of impedance [42].…”

Section: Electrical Impedance Spectroscopy (Eis) Analysismentioning

confidence: 99%

Effect of calcination on structural, morphological and photoelectrochemical performance of SnO2/TiO2 nanostructure films

et al. 2015

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Nanostructured multilayer TiO2–Ge films with quantum confinement effects for photovoltaic applications

Cited by 33 publications

References 22 publications

Characterisation Studies of the Structure and Properties of As-Deposited and Annealed Pulsed Magnetron Sputtered Titania Coatings

Characterisation Studies of the Structure and Properties of As-Deposited and Annealed Pulsed Magnetron Sputtered Titania Coatings

Recent developments in TiO2 as n- and p-type transparent semiconductors: synthesis, modification, properties, and energy-related applications

Effect of calcination on structural, morphological and photoelectrochemical performance of SnO2/TiO2 nanostructure films

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