Incorporating optical techniques in electron microscopy for comprehensive characterization of individual nanostructures

author: Min Gao, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing, China
published: Dec. 3, 2008,   recorded: October 2008,   views: 5239


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The purpose of this informal talk is to introduce briefly some new additions to the research group at Peking University and seek more future collaborations with JSI.

Optical techniques (e.g., luminescence and Raman spectroscopy) can provide rich information on semiconductor properties (band structure, phonon structure, confinements, etc.), which are complementary to electron microscopy techniques. Initial efforts have been carried out to combine submicron optical techniques and in situ nanoprobe technique in electron microscopy to carry out comprehensive characterization of individual semiconductor nanostructures.

In the first approach, we attach individual suspended semiconductor nanowires or nanorods to nanometer sized metal tips, which are compatible for different instruments, such as scanning electron microscope (SEM), transmission electron microscope (TEM) and microphotoluminescence (PL). Thus optical (PL), microstructural (SEM and TEM) and electrical (nanoprobe technique inside SEM) characterization can be carried out on the same 1­D nanostructure. Our results on in situ annealed ZnO nanowires show conclusive correlations among defect­related green emission, redshift of the near band edge emission, carrier density and oxygen deficiency. This highly flexible technique also enables angular dependent microphotoluminescence measurements on individual suspended ZnO nanorods. In the second approach, we combine optical fiber probe with the nanoprobe technique in SEM to achieve comprehensive characterization of optoelectronic nanotructures inside a single chamber.

The nanoprobe technique, employing sharp metal tips, is used for nanostructure manipulation and electrical measurement. The fiber probe, coupled to a spectrometer or a laser and controlled by a nanomanipulator, allows local optical detection or excitation. Using in situ light emitter and photodetector based on individual nanostructures, we demonstrate that above technique with high flexibility and efficiency can play an important role in building prototype optoelectronic devices and selectingsuitable nanostructures for device purposes.

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