Materials science is an interdisciplinary field that investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. Materials science aims at creating or transforming existing materials as well as enhancing materials to give better performance for particular applications.
Charge carrier dynamics in semiconductors
Charge carrier dynamics in semiconductors are determined by the architecture and function of the respective device and directly reflect the nature and quality of wafer materials. This makes precise and efficient measurement techniques of the free charge carrier lifetime essential for characterizing these systems. For particular classes of semiconductors, the characteristic charge carrier lifetime is highly dependent on the nature and dimensions of the materials and interfaces involved. Furthermore, surface effects, passivation and the energy transfer efficiency of sensitizers as well as the presence of dopants, impurities and defect sites can introduce significant variations in this parameter. Since the photoluminescence of semiconductors is a direct monitor of the charge carrier dynamics, the general methodology of time-resolved photo-luminescence (TRPL) via time-correlated single photon counting (TCSPC) and the periphery technology are highly suited for the analysis of the phenomena that determine fast charge carrier dynamics in a semiconductor. As a result, the mechanism that determines the charge carrier dynamics within a particular system can be characterized directly down to the sub-nanosecond time scale.
Direct observation of charge carrier dynamics
The general methodology of time-resolved photoluminescence can be expanded by lifetime imaging of the charge carrier dynamics. This can be exploited for, e.g., determining the effect of carrier diffusion and its influence on the total lifetime measured in conjunction with intensity dependent photoluminescence lifetimes measurements. It brings an exceptional component to semiconductor analysis with respect to material and architectural substructures, spatial inhomogenities and process dependent morphology. Using TRPL imaging, charge carrier diffusion processes and the effect of localized inhomogeneities and defect sites can be identified. With this multi-dimensional approach, a versatile and powerful methodology for the analysis of semiconductor materials can be achieved.
Upconversion photoluminescence of lanthanide complexes
Lanthanide-doped upconversion materials have great potential for applications such as fluorescence labels for in vitro bioimaging, as lighting sources in optical devices or as up-shifting layers in solar cells. These materials absorb light in the near infrared (NIR) spectral region (typically at ca. 980 nm) and emit light in the visible range. The structure of the luminescence spectrum strongly depends on the composition of the upconversion material as well as on the excitation intensity. The FluoTime 300 spectrometer can achieve very high spectral resolution along with outstanding stray light rejection when equipped with double monochromators in both excitation and emission pathways. This configuration is therefore well suited to measure the rather weak upconversion luminescence from these highly scattering samples. The upconversion luminescence kinetics of lanthanide-doped materials can range from nanoseconds to milliseconds. Thus the FluoTime 300 spectrometer is ideally suited to study these materials as it can cover time spans from a few picoseconds to several seconds by using either Time-Correlated Single Photon Counting (TCSPC) or Multi-Channel Scaling (MCS).
Laser output injected into an amplifier or another laser
A seed laser is a laser whose output is injected into some amplifier or another laser. Seed lasers are typically combined with an amplifier in a master oscillator power amplifier configuration used for generating an output with high power. The seed laser approach is often superior to a direct high power laser as very often certain features of low power seed lasers such as short pulses, adjustable repetition rates or narrow spectral line widths are easier to obtain.