Within our facility, we employ Secondary Ion Mass Spectrometry (SIMS) and X-ray Photoelectron Spectroscopy (XPS) as advanced techniques for probing material surfaces at the atomic and molecular scale, offering high sensitivity to both trace element concentrations and chemical states. SIMS operates by bombarding a sample surface with a focused primary ion beam, leading to the sputtering of secondary ions that are subsequently mass-analyzed. This method is renowned for its exceptional sensitivity—often down to parts-per-billion (ppb) levels—for a wide variety of elements and isotopes. In particular, depth profiling by SIMS enables the reconstruction of concentration profiles, making it indispensable for the characterization of multilayer structures, dopant distributions in semiconductors, and diffusion processes in thin films.
XPS, by contrast, is based on the photoelectric effect: X-rays incident on a material cause the emission of core-level electrons, whose kinetic energies are analyzed to provide detailed information on elemental composition and chemical bonding. The technique is intrinsically surface-sensitive, probing depths of only a few nanometers, and it thus offers a powerful means of monitoring surface functionalization, oxidation states, and adsorbate species. In practice, XPS can distinguish, for example, between metallic, oxide, and hydroxide forms of a given element, or between different functional groups in organic thin films. In the context of nanomaterials, XPS is particularly valuable for characterizing ligands on nanoparticles, evaluating oxides on metallic nanostructures, and determining the chemical environment of dopants in complex matrices.
A distinctive strength of our laboratory lies in the synergistic in-situ use of SIMS and XPS. While SIMS affords unparalleled sensitivity and isotopic specificity, XPS complements it by resolving the chemical state of detected elements. For instance, in semiconductor heterostructures, SIMS can map the spatial distribution of dopants or impurities, whereas XPS can identify their chemical state. This combined approach is particularly crucial in advanced device architectures, such as three-dimensional integrated circuits, memristive devices, and perovskite-based optoelectronics, where subtle variations in chemical state and composition can have a disproportionate impact on performance and reliability.
Ion implantation is utilized in our lab for surface modification and for the fabrication of reference standards, enabling SIMS quantification for virtually any matrix–dopant combination. In the context of materials modification, ion implantation allows the controlled introduction of specific atomic species at well-defined depths and concentrations, often with nanometer-scale precision. This approach is routinely used to tailor electronic, optical, and magnetic properties, for example by introducing donors or acceptors in semiconductors, modifying refractive indices in optical materials, or creating defect centers in wide-bandgap crystals. In nanomaterials research, ion implantation can be leveraged to generate color centers in diamond or silicon carbide, to tune plasmonic resonances in metallic nanostructures, or to modify catalytic activity in transition-metal oxides.
From a metrological standpoint, ion-implanted standards are essential for quantitative SIMS. Since SIMS signal intensities depend not only on concentration but also strongly on matrix effects—such as bonding environment, sputter yield, and ionization probability—direct quantification is non-trivial. By preparing well-characterized standards via ion implantation, in which the dopant fluence and depth distribution are accurately known, calibration curves can be constructed to convert SIMS intensities into absolute concentrations for a given matrix–dopant pair. The ability to generate custom standards on demand significantly expands the range of materials and impurity systems that can be quantitatively analyzed, from traditional silicon-based devices to emerging materials such as two-dimensional (2D) semiconductors, complex oxides, and hybrid perovskites.
An Optically Detected Magnetic Resonance (ODMR) technique is under development, based on high-resolution confocal microscopy, for the characterization of materials relevant to quantum technologies and for applications in quantum sensing. ODMR exploits the coupling between electronic or spin states and optical transitions, enabling the readout of spin resonance signals through changes in photoluminescence intensity or spectrum under resonant microwave excitation. When combined with confocal microscopy, this approach offers diffraction-limited spatial resolution and the capability to address single quantum emitters or nanoscale ensembles. This platform is particularly well-suited for the investigation of solid-state spin defects, such as nitrogen-vacancy (NV) centers in diamond, divacancies in silicon carbide, or rare-earth ions in crystalline hosts, which are prime candidates for qubits, quantum memories, and nanoscale sensors of magnetic fields, temperature, and strain. For example, by monitoring the ODMR spectrum of an NV center, one can reconstruct the local magnetic field with nanometer spatial resolution and sensitivities down to the nanotesla regime, or detect minute temperature changes through shifts in the zero-field splitting. The confocal ODMR setup under development thus provides a powerful tool to evaluate defect charge states, spin coherence times, and environmental noise sources in candidate quantum materials, facilitating both materials discovery and device optimization.
A Cryogen-Free Dilution Refrigerator System, installed in a shielded environment, is employed for Positron Annihilation Spectroscopy (PAS) experiments over a temperature range extending from room temperature (RT) down to approximately 10 mK. PAS is an extremely sensitive probe of open-volume defects—such as vacancies, vacancy clusters, dislocations, and voids—within crystalline and amorphous solids. By injecting positrons into a sample and measuring either the lifetime of the positron–electron pair or the energy–momentum distribution of the emitted gamma rays upon annihilation, one can infer the size, concentration, and chemical environment of defects. The combination of PAS with ultra-low temperatures opens unique opportunities to study defect dynamics, charge-state transitions, and trapping phenomena in regimes where thermal activation is strongly suppressed. This cryogenic platform further facilitates transport measurements, noise spectroscopy and electromagnetic characterization at ultra-low temperatures, supporting investigations into both fundamental and applied aspects of nanosystems and nanostructured materials.
Electromagnetic characterization, including microwave spectroscopy, impedance measurements, and mutual inductance techniques, can further elucidate the dynamic response of materials in the low-frequency to gigahertz regime. Such measurements are particularly relevant for superconducting qubits, resonators, and hybrid quantum devices, in which dielectric losses, two-level system defects, and surface magnetism can severely limit coherence times and device performance. The capability to correlate ultra-low-temperature transport and electromagnetic properties with structural and chemical information obtained from SIMS, XPS, ion implantation studies, ODMR, and PAS represents a significant advantage of the laboratory, enabling a genuinely multimodal characterization strategy.
The integrated infrustructure provided by the laboratory supports both fundamental research—aimed at understanding the interplay between composition, structure, defects, and emergent properties—and applied research focused on the development and optimization of next-generation devices in nanoelectronics, spintronics, photonics, and quantum technologies. Through the combination of complementary techniques and cryogenic platforms, the laboratory is positioned as a versatile hub for both academic and industrial collaborations, where complex materials challenges can be addressed by correlating structural, chemical, electronic, and quantum-level information within a single, coherent experimental framework.
The following experimental techniques are available:
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