This PDF file contains the front matter associated with SPIE Proceedings Volume 11990, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Graphite has been often used as an electrode for batteries due to its resistance to corrosion and good electrical conductivity. Graphite electrodes was obtained by modifying the surface of a synthetic diamond substrate, but the uniformity of the graphitized area on the surface should be monitored. Hall measurement was generally used to evaluate the performance of electrodes, but it can only provide the average conductivity between the electrodes. In this study, we performed Raman scattering micro-spectroscopy to evaluate the conductivity of graphite with non-destructive, noncontact measurements and the high spatial resolution. The samples in this study was graphitized from CVD-grown diamond by thermal treatment with deposition of the catalytic metal Nickel. Raman spectra were measured in the Ni-deposited and non-Ni-deposited regions, and it can be seen that only the catalytically reacted area was graphitized from diamond. The sample with graphite-derived peaks in Raman spectrum also showed symmetrical voltamogram in electrolysis measurements. However, for the samples with insufficient modification to graphite, the electrolysis voltamogram were asymmetric. It was possible to predict the properties of the redox reaction between the electrode and the solution in electrochemistry from the Raman spectra. These results verify the production of graphite-diamond hybrid electrodes.

We present on our progress in the design, fabrication, and characterization of light-emitting transistors based on twodimensional materials (2D-LETs) and top-gate dielectrics that enable voltage-controlled wavelength-agile light emission spanning from the visible (VIS) to the near-infrared (NIR) spectrum at room temperature. Monolayer transition metal dichalcogenide (TMD) devices (e.g. MoS₂, MoSe₂, WS₂, WSe₂) emit in the VIS-NIR range with respect to their direct bandgaps. The wavelength of the light emission from the TMD devices may be tuned to the NIR by reducing their direct bandgaps via the giant Stark Effect.

The optical fiber sensing field is in continuous seek of new processing methods, light localization structures and transduction mechanisms for developing devices with novel functionalities and/or improved performance, while targeting existing or emerging application fields. Herein, we are reviewing work performed on the imprinting of optical resonators, onto optical fibers using multi-photon, three-dimensional lithography. Two major resonating cavity designs are presented: hollow Fabry-Perot resonators imprinted onto the endface of optical fibers, and micro-ring resonators attached onto micronic diameter optical fiber tapers; both types of devices operate at the 1.5μm spectral band. Results are presented on the design, spectral characterization and simulation of those hybrid type of photonic devices, while their sensing capabilities are exemplified in the tracing of organic solvent vapors, which upon case can reach sub-ppm detectivity levels.

The optical and electrical properties of two-dimensional transition metal dichalcogenide materials (2D-TMDs) are determined by their exciton dynamics. When the thickness of these materials is thinned down to a single layer, the spatial confinement makes the impact of exciton dynamics on the functionality of 2D-TMD-based devices even more important. Here, we present an investigation of the dynamics of formation and decay of the lowest excitons 2D-TMD monolayers. Excitation energy-dependent transient absorption studies indicated that the exciton formation time increases linearly from ~150 fs upon resonant excitation to ~500 fs following excitation that is ~1.1 eV above the bandgap. This dependence is attributed to the time it takes highly excited electrons in the conduction band (CB) to relax to the CB minimum (CBM) and contribute to the formation of the X_A exciton. Additionally, excitation energy dependent studies suggested that the exciton average lifetime increases from ~10 ps in the case of resonant excitation to ~50 ps following excitation well above the band-gap. Furthermore, studies of the dependence of exciton dynamics on the excitation density suggested that exciton decay in these materials is dominated by defect-assisted recombination (DAR).

Silicon photonics is a technology that aims at improving state-of-the-art optical communication systems through high performance lasers, which currently rely mostly on III-As materials grown on silicon-on-insulator platforms and, in the future, on InAs quantum dots (QDs). In this work, we present an extensive investigation on the properties of defects in IIIAs layers as a function of the presence/absence of QDs layers and of dislocation density. By using deep level transient spectroscopy (DLTS), we analyzed two kinds of devices: GaAs diodes grown on Si (high dislocation density) and GaAs diodes grown on GaAs (low dislocation density) with QDs embedded. Our study showed that the device grown on Si exhibits four distinct traps (3 electron and 1 hole trap), whereas the sample grown on GaAs contains only one hole trap, which is in common among the two devices. These defects are placed in proximity of the semiconductor midgap, therefore they can act as efficient non-radiative recombination centers (NNRCs). The analysis of the capture kinetics showed that two of the traps are associated to point defects and that the remaining two seem to be related to point defects arranged along a dislocation. According our investigation, embedding QDs into the pin structure does not lead to the generation of additional defects, since the only measurable trap in the device with QDs is common to both samples. Finally, a tentative association of the detected traps with previous reports revealed that the dominant traps may be associated with native III-As defects or oxygen-related complexes.

Photothermal microscopy is a powerful method for investigating biological systems and solid state materials. Using a modulated pump to excite the sample, a continuous probe beam monitors the change in the refractive index of the sample due to the modulated heating. These experiments are typically performed at high frequencies to reduce the 1/f noise, achieving a higher signal to noise ratio. In this paper, we explore how the resolution and sensitivity of the photothermal experiments change when the modulation frequency is brought down below 100kHz. In the instance that the pump and probe are cofocused at the sample, the resolution is determined by the size of the pump beam. On the other hand, when a widefield pump is used, significant broadening occurs for frequencies under 20kHz. This broadening is attributed to thermal diffusion. However, the amount of broadening is less than that expected from the thermal diffusion length, which is about 1.7µm at 10kHz for nanoparticles in glycerol. We also explore the situation where the point spread functions of the pump and probe beams are smaller than the particle size as well as how the penetration depth depends on the properties of the pump and probe beams.

In order to enable the silicon photoelectric detector to be easily integrated with CMOS components in the circuit, which is necessary for commercial demand, the thin film structure on the surface can enhance the electrical and optical characteristics of the devices. Here we have used metal nanoscale thin film structure to study the electrical and optical performance in silicon-based detector. We deposited a thin film of Cr on n-type Silicon (n-Si) with an electron-beam evaporator. The main purpose of this step is to generate the active layer on device, and this was followed by annealing using rapid thermal processer in temperature range from 500°C to 700°C. The performed experiments shows that the device use IPE effect to collect hot carriers and by rapid thermal annealing, allowing carriers to easily cross over and generate detection signals.

Titanium nitride (TiN) nanoparticles (NPs) prepared by methods of laser ablation in liquids present a novel object, which promises attractive biomedical applications. Here, we review our recent advances in the elaboration of femtosecond laser ablation technique from a TiN target in liquid medium (here, isopropanol) to maximize the efficiency of TiN NPs synthesis and optimize their characteristics. Our experiments showed that the synthesis productivity is dependent on lateral velocity of laser beam scanning during laser ablation with the achievement of productivity saturation at a certain relatively high velocity. The observed phenomenon was attributed to the interaction of laser pulses with cavitation bubbles generated during the ablation process. In addition, we assessed photo heating properties of the synthesized TiN NPs in the near-IR range. It was found that TiN NPs with sizes in 20-50 nm range have the highest heating rate and can be heated to maximal temperatures. As demonstrated by our recent tests in vitro and in vivo, this size range is optimal for biomedical applications, which promises successful applications of these nanoparticles in phototherapy and imaging modalities.

Newly emerging nanomaterials promise a major advancement of methods of nuclear and radiative medicine for cancer treatment, as they can be used as carriers of diagnostic or therapeutic radionuclides, contrast agents in nuclear imaging modalities (PET, SPECT) or sensitizers of radiative therapies (X-ray, ion beams, etc.). However, nanotechnology-based approaches have reported a limited success so far due to a lack of suitable functional nanoformulations, which are safe, non-toxic, excretable from the body and have favorable pharmacokinetics for effective accumulation in the tumor. As follows from the results of our on-going research activities, many of the above-stated problems can we solved by the employment of nanomaterials fabricated by clean laser-ablative synthesis. Here, we review our recent data on some promising nanomaterials, prepared by this method, including biodegradable silicon (Si) nanoparticles (NPs), ¹⁵²Sm-enriched samarium oxide NPs, and elemental bismuth (Bi) NPs, which can be used either as carriers/agents in radionuclide therapy, or sensitizers in radiative diagnostics or therapy. Advantages of proposed approach include exceptional purity and flexibility in synthesizing of NPs of required physico-chemical parameters (controlled size, shape, composition, and surface conditioning of NPs). Advances in laser-ablative fabrication of novel nanomaterials open up avenues for future implementations of nuclear and radiative medicine approaches for safe and efficient theranostics of tumors and metastasis.