Browsing by Subject "Carrier concentration"

Article

Concentration and excitation effects on the exciton dynamics of poly(3-hexylthiophene)/PbS quantum dot blend films

Tsokkou, Demetra; Itskos, Grigorios; Choulis, Stelios A.; Yarema, M.; Heiss, W.; Othonos, Andreas S. (2013)

The dynamics of photoexcitations in hybrid blends of poly(3-hexylthiophene) (P3HT) conjugated polymer donor and oleic-acid capped lead sulfide (PbS) quantum dot (QD) acceptors of different concentrations - for light ...

Article

Electronic Structure and Thermoelectric Properties of Pseudoquaternary Mg2Si1-x-ySnxGey-Based Materials

Kutorasinski, K.; Tobola, J.; Kaprzyk, S.; Khan, A. U.; Kyratsi, Theodora (2014)

A theoretical study is presented on complex pseudoternary Bi-doped Mg2Si1-x-ySnxGey materials, which have recently been revealed to reach high thermoelectric figures of merit (ZT) of ∼1.4. Morphological characterization ...

Article

Femtosecond carrier dynamics of Inx Ga1-x N thin films grown on GaN (0001): Effect of carrier-defect scattering

Lioudakis, Emmanouil E.; Othonos, Andreas S.; Iliopoulos, Eleftherios; Tsagaraki, K.; Georgakilas, A. (2007)

Ultrafast carrier dynamics in ultrathin Inx Ga1-x N ternary alloys were investigated in detail, using femtosecond transient differential optical absorption measurements. Measurements were performed with probing wavelengths ...

Article

Indium oxide as a possible tunnel barrier in spintronic devices

Androulakis, J.; Gardelis, S.; Giapintzakis, John; Gagaoudakis, E.; Kiriakidis, G. (2005)

We report the growth of ultra-thin indium oxide layers using the dc-magnetron sputtering method. We demonstrate that good quality tunnel barriers made of indium oxide can be routinely fabricated and employed in spintronic-related ...

Article

Light-induced mobility enhancement in delta-doped GaAs/In0.26Ga0.74As/GaAs quantum wells grown by molecular beam epitaxy on GaAs(001)

Zervos, Matthew; Elliott, M.; Westwood, D. I. (1999)

Persistent photoconductivity in 80 angstroms strained GaAs/In0.26Ga0.74As/GaAs quantum wells was investigated by measuring the Shubnikov de Haas and Hall effects at 4.2 K. The quantum wells were grown by molecular beam ...

Article

Modification of thermoelectric properties using insertion techniques

Hatzikraniotis, E.; Kyratsi, Theodora; Chrissafis, K.; Paraskevopoulos, K. M. (1999)

In this work is presented the application insertion techniques for the modification of the performance of thermoelectric materials. The results indicate that in cases as in Bi2Se3 compounds where insertion of foreign species ...

Article

Probing carrier dynamics in implanted and annealed polycrystalline silicon thin films using white light

Lioudakis, Emmanouil E.; Othonos, Andreas S.; Nassiopoulou, Androula Galiouna (2006)

Polycrystalline silicon thin film samples implanted and annealed at various temperatures have been studied using ultrafast laser pulse excitation. Nondegenerate pump-probe technique has been utilized to investigate carrier ...

Article

Properties of Si-doped GaN and AlGaN/GaN heterostructures grown by RF-MBE on high resistivity Fe-doped GaN

Iliopoulos, E.; Zervos, Matthew; Adikimenakis, A.; Tsagaraki, K.; Georgakilas, A. (2006)

Silicon-doped GaN epilayers and AlGaN/GaN heterostructures were developed by nitrogen plasma-assisted molecular beam epitaxy on high resistivity iron-doped GaN (0001) templates and their properties were investigated by ...

Article

SAXS Investigation of ABC Triblock Star Terpolymers in Aqueous Solution

Castelletto, V.; Hamley, I. W.; Triftaridou, Aggeliki I.; Patrickios, Costas S. (2004)

The structure of three different ABC triblock star terpolymers in aqueous solution has been investigated by small-angle x-ray scattering (SAXS). The form factor was modeled using an analytical expression for a Gaussian ...

Article

Symmetry of differential optical responses of normal and superconducting phases in single-crystal YBCO

Studenmund, W. R.; Fishman, I. M.; Kino, G. S.; Giapintzakis, John (1995)

We measured differential optical reflectivity (DOR) of YBCO single domains. DOR measurements reject the temperature independent bulk reflectivity and reveal dR dT. These measurements detect the superconducting transition, ...

Article

Temporal evolution of effects of ultrafast carrier dynamics in In 0.33Ga0.67N: Above and near the bandgap

Lioudakis, Emmanouil E.; Iliopoulos, Eleftherios; Georgakilas, A.; Othonos, Andreas S. (2007)

Ultrafast carrier dynamics in the In0.33Ga0.67N epilayer were investigated in detail, using femtosecond transient differential non-degenerate optical absorption measurements. Following an excitation at 400 nm with fluence ...

Article

Thermoelectric properties and site-selective Rb+/K+ distribution in the K2-xRbxBi8Se13 series

Kyratsi, Theodora; Chung, D. Y.; Ireland, J. R.; Kannewurf, C. R.; Kanatzidis, M. G. (2003)

β-K2Bi8Se13 possesses promising thermoelectric properties whereas Rb2Bi8Se13 does not. The formation of solid solutions between these two compounds was attempted to study the alkali metal distribution in the structure and ...

Article

Thermoelectric properties of nanocrystalline PbTe synthesized by mechanical alloying

Papageorgiou, Ch; Hatzikraniotis, E.; Lioutas, Ch B.; Frangis, N.; Valassiades, O.; Paraskevopoulos, K. M.; Kyratsi, Theodora (2010)

In this work, nanocrystalline lead telluride powder was synthesized from high-purity elements by mechanical alloying by means of a planetary ball-milling procedure. The milling medium was tungsten carbide, and the diameter ...

Article

Ultrafast carrier dynamics on conjugated poly(3-hexylthiophene)/[6,6]- phenyl C61 -butyric acid methyl ester composites

Lioudakis, Emmanouil E.; Othonos, Andreas S.; Alexandrou, Ioannis; Hayashi, Y. (2007)

The authors have studied ultrafast carrier dynamics on poly(3- hexylthiophene)/[6,6]- phenyl C61 -butyric acid methyl ester (PCBM) composites up to 50% PCBM concentration. They have resolved the exciton intraband relaxation ...