Pushing the limit of confocal polarized Raman microscopy

2007 ◽  
Vol 85 (10) ◽  
pp. 806-815 ◽  
Author(s):  
François Lagugné-Labarthet

Raman microscopy has emerged as a powerful technique to characterize anisotropic materials with sub micro meter resolution. The use of polarized light allows one to obtain precise information about the local organization of the relevant molecular groups through the determination of the most probable distribution function. Such polarization analysis can be conducted under a confocal microscope, but caution must be exercised because of the use of objectives of high numerical value. The molecular orientation can be effectively correlated with the topography of the sample when atomic force microscopy experiments are conducted on the same object. In the present review paper, we present Raman imaging results that have been conducted on mesostructured polymer surfaces and on a single isolated semiconductor nanowire.Key words: Raman spectroscopy, confocal microscopy, orientation parameters, azopolymers, nanowires.

2010 ◽  
Author(s):  
Juergen Sawatzki ◽  
Carsten Wehlack ◽  
Wulff Possart ◽  
Andrea Thoene ◽  
Matthias Hannss ◽  
...  

2007 ◽  
Vol 93 (1) ◽  
pp. 202-207 ◽  
Author(s):  
Jose Carlos Rodríguez Hernández ◽  
Manuel Salmerón Sánchez ◽  
José Miguel Soria ◽  
José Luis Gómez Ribelles ◽  
Manuel Monleón Pradas

1998 ◽  
Vol 512 ◽  
Author(s):  
N. Grandjean ◽  
M. Leroux ◽  
J. Massies ◽  
M. Mesrine ◽  
P. Lorenzini

ABSTRACTAmmonia as nitrogen precursor has been used to grow III-V nitrides by molecular beam epitaxy (MBE) on c-plane sapphire substrates. The efficiency of NH3 has been evaluated allowing the determination of the actual V/III flux ratio used during the GaN growth. The effects of the V/III ratio variation on the GaN layer properties have been investigated by photoluminescence (PL), Hall measurements, atomic force microscopy (AFM), and secondary ion mass spectroscopy (SIMS). It is found that a high V/III ratio leads to the best material quality. Optimized GaN thick buffer layers have been used to grow GaN/AlGaN quantum well (QW) heterostructures. Their PL spectra exhibit well resolved emission peaks for QW thicknesses varying from 3 to 15 monolayers. From the variation of the QW energies as a function of well width, a piezoelectric field of 450 kV/cm is deduced.


2015 ◽  
Vol 1754 ◽  
pp. 69-74
Author(s):  
Ravi Gaikwad ◽  
Tinu Abraham ◽  
Aharnish Hande ◽  
Fatemeh Bakhtiari ◽  
Siddhartha Das ◽  
...  

ABSTRACTAtomic force microscopy is employed to study the structural changes in the morphology and physical characteristics of asphaltene aggregates as a function of temperature. The exotic fractal structure obtained by evaporation-driven asphaltene aggregates shows an interesting dynamics for a large range of temperatures from 25°C to 80°C. The changes in the topography, surface potential and adhesion are unnoticeable until 70°C. However, a significant change in the dynamics and material properties is displayed in the range of 70°C - 80°C, during which the aspahltene aggregates acquire ‘liquid-like’ mobility and fuse together. This behaviour is attributed to the transition from the pure amorphous phase to a crystalline liquid phase which occurs at approximately 70°C as shown by using Differential Scanning Calorimetry (DSC). Additionally, the charged nature of asphaltenes and bitumen is also explored using kelvin probe microscopy. Such observations can lead to the development of a rational approach to the fundamental understanding of asphaltene aggregation dynamics and may help in devising novel techniques for the handling and separation of asphaltene aggregates using dielectrophoretic methods.


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