On the field effect in polycrystalline CdSe thin-film transistors

Calster, André Van; Vanfleteren, Jan; Rycke, I. De; Baets, Johan De

doi:10.1063/1.341518

Cited by 25 publications

(12 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It has a rather rich and complex band structure and a characteristic combination of properties that make this material of pivotal relevance to energy conservation problems, thin film transistors and sensor technologies, acousto-optical devices etc. [18][19][20][21][22][23][24][25]. All these properties and applicative potential of the studied system make it almost a prototypical semiconductor for a wide variety of applications and fundamental scientific issues.…”

Section: Introductionmentioning

confidence: 99%

Sonochemically assisted colloidal route to CdSe quantum dot assemblies: an alternative way to further fine-tune the size-dependent properties

Pejova

Bineva

2016

J Mater Sci: Mater Electron

View full text Add to dashboard Cite

Continuous-wave heterogeneous sonochemical method was developed to synthesize 3D assemblies composed by QDs of metastable (cubic) modification of CdSe with sphalerite structural type. 3D QD assemblies were deposited in thin film form and as bulk precipitates. Structure, surface morphology, optical absorption as well as charge carriers' and phonon confinement effects were studied in details. The average nanocrystal radius, calculated by the Scherrer and Williamson-Hall methods, diminishes from 2.7 nm for samples synthesized by conventional colloidal chemical route to 2.0 nm for samples synthesized by sonochemical route. Upon post-deposition thermal annealing this value increases to 12.0 nm. QD size decrease is followed by increase of the uni-directional lattice strain and dislocation density (as defined by Hirsch), as well as by decrease of the lattice constant value. Previous findings were justified by analysis of X-ray diffraction peaks shape, which were found to be dominated by the particle size-distribution, instead of non-uniform strain. The energy of the fundamental direct C v 8 ! C c 6 interband electronic transition, computed from optical absorption data within parabolic approximation for the dispersion relation, shifts from 2.67 eV for sonochemically deposited samples and 2.08 eV for chemically deposited ones, to 1.77 eV upon post-deposition thermal treatment (close to the bulk value of 1.74 eV). The type of ''interband'' transitions does not change upon dimensionality reduce. Enhanced band gap energy blue shift upon average QD size decrease is followed by oscillator strength increase. Such trends were rationalized in terms of 3D confinement effects on charge carriers' motion. Experimentally observed band gap energies agree very well with the predictions of the effective mass model of Brus. The next direct interband electronic transition, from the spin-orbit split component of the valence band to the conduction band, has been detected and analyzed. The 1LO bands in the Raman spectra of chemically and sonochemically deposited samples appear at 206 and 204 cm -1 , as compared to the bulk value of 210 cm -1 . The extent of homogeneous broadening of the corresponding band is larger in sonochemically deposited samples, indicating enhanced frequency of phonon-phonon collisions in smaller QDs. The observed frequency shifts are dominated by phonon-dispersion terms, instead of lattice contraction.

show abstract

Section: Introductionmentioning

confidence: 99%

Sonochemically assisted colloidal route to CdSe quantum dot assemblies: an alternative way to further fine-tune the size-dependent properties

Pejova

Bineva

2016

J Mater Sci: Mater Electron

View full text Add to dashboard Cite

show abstract

“…Concerning the relevance of the chosen semiconductor system (CdSe), it is a member of A II B VI group of binary semiconductors. Characteristic combination of properties of this material (related mainly to its characteristic band structure) makes it of prime importance in energy conservation problems. − Cadmium selenide, especially deposited in thin film form, has found numerous applications, for example, as thin film transistors, gas sensing, , acousto-optical devices, vidicones, photographic photoreceptors, and so on. This semiconductor exists in two polymorph modifications: cubic and hexagonal, the first one being of sphalerite structural type, whereas the second one is of wurtzite type.…”

Section: Introductionmentioning

confidence: 99%

Nanostructured CdSe Films in Low Size-Quantization Regime: Temperature Dependence of the Band Gap Energy and Sub-Band Gap Absorption Tails

Pejova

Abay

2011

J. Phys. Chem. C

View full text Add to dashboard Cite

Temperature dependence of the band gap energy and sub-band gap absorption tails in 3D assemblies of close packed weakly quantized CdSe quantum dots deposited as thin films was studied. The range from cryogenic temperatures (∼10 K) up to 340 K was covered. Excitonic absorption peaks were not observed even at temperatures as low as 11 K, which was attributed to the finite particle size distribution and interdot electronic coupling effects. The temperature coefficient of the band gap energy of the nanostructured films of 9.4 Â 10 À4 eV K À1 is higher by a factor of 1.35 than the corresponding value for the bulk CdSe specimen. As compared to the case of films constituted of strongly quantized ZnSe QDs, where the factor α nanocrystal /α bulk was found to be 1.82 (Pejova, B.; Abay, B.; Bineva, I. J. Phys. Chem. C 2011, 115, 37), the present findings imply that this ratio increases upon enhancement of size quantization effects in semiconductor nanocrystals. Analysis of the temperature-dependent optical absorption data within the Bose-Einstein model implies that no phonon confinement effects influence the phonon spectrum in the presently studied material due to the very small size-quantization effects. This situation is opposite to what we have recently found in the case of 3D arrays of strongly quantized ZnSe films. The characteristic Einstein temperature of the presently studied material corresponds to phonon frequency of about 220 cm À1 , in excellent agreement with the LO mode frequency of bulk CdSe (210À214 cm À1 ). It is demonstrated that the Urbach rule is valid in the presently studied nanostructured material in low size-quantization regime. Urbach energies are several times higher than the values characteristic for macrocrystalline materials, due to the relatively high degree of inherent structural disorder in the studied QD solids. At the same time, however, these values are approximately three times smaller than those reported for strongly quantized ZnSe films in our previous study. The dynamical (temperature-dependent) term accounts for only about 22% of the overall Urbach energy values, though this value is higher than the corresponding ratio in the case of strongly quantized ZnSe films.

show abstract

“…Here we apply the known expression, which was introduced by Levinson et al to describe performance of CdSe TFT [12,13], to the device transfer character. Deduction of the expression takes into account the influence of grain boundary barriers in the poly-crystalline channel, assuming the channel mobility is modified with gate voltage.…”

Section: Discussionmentioning

confidence: 99%

Fabrication and property study of thin film transistor using rf sputtered ZnO as channel layer

Yao

2005

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

On the field effect in polycrystalline CdSe thin-film transistors

Cited by 25 publications

References 10 publications

Sonochemically assisted colloidal route to CdSe quantum dot assemblies: an alternative way to further fine-tune the size-dependent properties

Sonochemically assisted colloidal route to CdSe quantum dot assemblies: an alternative way to further fine-tune the size-dependent properties

Nanostructured CdSe Films in Low Size-Quantization Regime: Temperature Dependence of the Band Gap Energy and Sub-Band Gap Absorption Tails

Fabrication and property study of thin film transistor using rf sputtered ZnO as channel layer

Contact Info

Product

Resources

About