TY  - JOUR
A1  - Pietsch, Ullrich
A1  - Grenzer, Jörg
A1  - Grigorian, Souren A.
A1  - Weyers, Markus
A1  - Zeimer, Ute
A1  - Feranchuk, S.
A1  - Fricke, J.
A1  - Kissel, H.
A1  - Knauer, A.
A1  - Tränkle, G.
T1  - Nanoengineering of lateral strain-modulation in quantum well heterostructures
N2  - We have developed a method to design a lateral band-gap modulation in a quantum well heterostructure. The lateral strain variation is induced by patterning of a stressor layer grown on top of a single quantum well which itself is not patterned. The three-dimensional (3D) strain distribution within the lateral nanostructure is calculated using linear elasticity theory applying a finite element technique. Based on the deformation potential approach the calculated strain distribution is translated into a local variation of the band-gap energy. Using a given vertical layer structure we are able to optimize the geometrical parameters to provide a nanostructure with maximum lateral band-gap variation. Experimentally such a structure was realized by etching a surface grating into a tensile-strained InGaP stressor layer grown on top of a compressively strained InGaAs-single quantum well. The achieved 3D strain distribution and the induced band-gap variation are successfully probed by x-ray grazing incidence diffraction and low-temperature photoluminescence measurements, respectively
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Pietsch, Ullrich
A1  - Grigorian, Souren A.
A1  - Grenzer, Jörg
A1  - Feranchuk, S.
A1  - Zeimer, Ute
T1  - Grazing-incidence diffraction study of strain-modulated single quantum well nanostructures
Y1  - 2003
ER  - 
TY  - JOUR
A1  - Pietsch, Ullrich
A1  - Grigorian, Souren A.
A1  - Grenzer, Jörg
A1  - Vartanyants, Ivan A.
T1  - Thermal diffuse scattering in grazing incidence diffraction
Y1  - 2003
ER  - 
TY  - JOUR
A1  - Pietsch, Ullrich
A1  - Zeimer, Ute
A1  - Grenzer, Jörg
A1  - Grigorian, Souren A.
A1  - Fricke, J.
A1  - Gramlich, S.
A1  - Bugge, F.
A1  - Weyers, Markus
A1  - Trankle, G.
T1  - Influence of lateral patterning geometry on lateral carrier confinement in strain-modulated InGaAs- nanostructures
Y1  - 2003
ER  - 
TY  - JOUR
A1  - Zen, Achmad
A1  - Saphiannikova, Marina
A1  - Neher, Dieter
A1  - Grenzer, Jörg
A1  - Grigorian, Souren A.
A1  - Pietsch, Ullrich
A1  - Asawapirom, Udom
A1  - Janietz, Silvia
A1  - Scherf, Ullrich
A1  - Lieberwirth, Ingo
A1  - Wegner, Gerhard
T1  - Effect of molecular weight on the structure and crystallinity of poly(3-hexylthiophene)
N2  - Recently, two different groups have reported independently that the mobility of field-effect transistors made from regioregular poly(3-hexylthiophene) (P3HT) increases strongly with molecular weight. Two different models were presented: one proposing carrier trapping at grain boundaries and the second putting emphasis on the conformation and packing of the polymer chains in the thin layers for different molecular weights. Here, we present the results of detailed investigations of powders and thin films of deuterated P3HT fractions with different molecular weight. For powder samples, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to investigate the structure and crystallization behavior of the polymers. The GPC investigations show that all weight fractions possess a rather broad molecular weight distribution. DSC measurements reveal a strong decrease of the crystallization temperature and, most important, a significant decrease of the degree of crystallinity with decreasing molecular weight. To study the structure of thin layers in lateral and vertical directions, both transmission electron microscopy (TEM) and X-ray grazing incidence diffraction (GID) were utilized. These methods show that thin layers of the low molecular weight fraction consist of well-defined crystalline domains embedded in a disordered matrix. We propose that the transport properties of layers prepared from fractions of poly(3-hexylthiophene) with different molecular weight are largely determined by the crystallinity of the samples and not by the perfection of the packing of the chains in the individual crystallites
Y1  - 2006
UR  - http://pubs.acs.org/doi/full/10.1021/ma0521349
U6  - https://doi.org/10.1021/Ma0521349
ER  -