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Scientific Report 2007-2009
Laboratories and Facilities of the Department of Physics
L9. Semiconductors and Optical Properties of Solids Lab
Since its foundation, the laboratory of Semiconductors and Optical Properties of Solids has been engaged in research on
the electronic and optical properties of semiconductors of interest in the fields of Information and Communication Technology
and renewable energies. Si and III-V compounds under different type of external perturbations (e.g. high magnetic field,
stress, excitation power density) have been the main objects of investigation. Either bulk material or heterostructures grown
by molecular beam epitaxy (quantum wells wires) or self assembling (quantum dots) by national or international laboratories
have been investigated. In the last ten years the interest of the laboratory has been focused on dilute nitrides and on the
effect hydrogen has on the electronic and structural properties of these compounds. More recently, we have shown that the
hydrogen induced effects can be exploited to achieve nanostructures with shape, size, and density arbitrarily designed in
the sample growth plain by a novel technique, which avoids major drawbacks typical of standard top-down or bottom-up
procedures.
A great variety of light sources, monochromators and detectors available in the laboratory permits to operate from the
(a)
(b)
Figure 1: (a) Optical table with apparatus for photoluminescence and Raman measurements (both micro and macro) in the
near-UV to near-IR energy range. (b) Apparatus for irradiation with low-energy atoms of samples maintained at different
temperatures.
near ultraviolet to mid-infrared energy range on two different optical tables.
Light sources are: a 2 W Coherent Ar laser, an 8 W Coherent Verdi diode laser, a 1 W Ti-sapphire tunable laser and a
Coherent MBD 266 frequency doubler pumped by the Verdi laser, high pressure Hg and Xe lamps. A 1 m McPherson single
monochromator, a 0.75 m Acton double monochromator, and a 0.3 m Jobin-Yvon single monochromator are also available,
together with detectors including a Princeton Si CCD and an InGaAs linear array, a Hamamatsu photomultiplier with an UV
extended GaAs cathode for single photon counting, an ADC ultrapure Ge detector, GaSb, InAs, PbS detectors, and related
control electronics. Eventually, samples can be cooled down to liquid helium temperatures in two closed cycle cryostats
or in two exchange gas cryostats, one of which equipped with magnetic fields up to 14 T. In order to measure the optical
properties of single nanostructures, the laboratory has been recently equipped with a microscope for micro-photoluminescence
and micro-Raman measurements and a He continuous-flow optical-cryostat whose piezoelectric movements permit to displace
samples at liquid helium temperature by 8 mm maximum in the plane perpendicular to the microscope optical axis, with a
resolution of a few nanometers. Finally, samples can be irradiated at temperatures ranging from room temperature to 600
C with beams of atomic hydrogen or other gases whose energy goes from a minimum of 50 eV to a maximum of 1500 eV.
Related research activities: C31,C32.
Sapienza Università di Roma 183 Dipartimento di Fisica