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A novel single-step, laser-induced and solution-based process is presented for synthesizing complex hybrid metal/carbon nanostructures. The process relies on simply illuminating the interface between a substrate and a liquid solution of the supramolecular complex [Au13Ag12(C2Ph)20(PPh2(C6H4)3PPh2)3][PF6]5 (hereinafter abbreviated as SMC) with an unfocussed He–Cd laser having a wavelength of 325 nm and an intensity of I = 0.5 W/cm2. The process results in hybrid nanostructures of well-controlled morphology: nanoparticles (NP) and 2D flakes, which may also grow jointly to form 3D morphologically complex multipetal ‘flower-like’ structures. At the atomic scale, the obtained metamaterials are complex in composition and structure, i.e., they contain bimetallic Au–Ag nanoclusters of diameter 3–5 nm incorporated inside a carbonaceous matrix. This matrix can be amorphous or crystalline, and the details of the compositional outcome can be controlled and steered by the laser deposition parameters. Au–Ag nanoclusters show plasmonic behavior including the enhancement of electromagnetic fields of visible light. This leads to the enhancement of Raman scattering by the Au–Ag nanoparticle ensemble within the carbonaceous matrix. This enables a 3D architecture for stimulating surface-enhanced Raman scattering (SERS).

Vertically aligned hexagonal InN nanorods were grown mask-free by conventional metal-organic vapor phase epitaxy without any foreign catalyst. The In droplets on top of the nanorods indicate a self-catalytic vapor-liquid-solid growth mode. A systematic study on important growth parameters has been carried out for the optimization of nanorod morphology. The nanorod N-polarity, induced by high temperature nitridation of the sapphire substrate, is necessary to achieve vertical growth. Hydrogen, usually inapplicable during InN growth due to formation of metallic indium, and silane are needed to enhance the aspect ratio and to reduce parasitic deposition beside the nanorods on the sapphire surface. The results reveal many similarities between InN and GaN nanorod growth showing that the process despite the large difference in growth temperature is similar. Transmission electron microscopy, spatially resolved energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy have been performed to analyze the structural properties. Spatially resolved cathodoluminescence investigations are carried out to verify the optical activity of the InN nanorods. The InN nanorods are expected to be the material of choice for high-efficiency hot carrier solar cells.

As a result of its indirect bandgap, emitting photons from silicon in an efficient way remains challenging. Silicon light emitters that can be integrated seamlessly on a CMOS platform have been demonstrated; however, none satisfies an ensemble of key requirements such as a small footprint, room temperature operation at low voltages, and emission of narrow and polarized lines with a high spectral power density in the near infrared range. Here, we present an all silicon electrically driven light emitting diode that consists of an inversely tapered halfellipsoidal silicon photonic resonator containing a p n junction used to excite whispering gallery modes WGMs inside the resonator. Under low voltage operation at room temperature, such a photonic silicon light emitting diode exhibits a band edge emission 900 1300 nm with a wall plug efficiency of 10 amp; 8722;4. The emitted spectrum is amplified in multiple WGMs and shows peaks that are polarized and have linewidths amp; 916; amp; 955; as narrow as 0.33 nm and spectral power densities as high as 8 mW cm amp; 8722;2 nm amp; 8722;1. Considering its small footprint of amp; 8764;1 amp; 956;m and remarkable emission characteristics, this silicon light source constitutes a significant step ahead toward fully integrated on chip silicon photonics

A fluorine free copper precursor, Cu(tbaoac)2 with the chemical sum formula CuC16O6H26 is introduced for focused electron beam induced deposition (FEBID). FEBID with 15 keV and 7 nA results in deposits with an atomic composition of Cu:O:C of approximately 1:1:2. Transmission electron microscopy proved that pure copper nanocrystals with sizes of up to around 15 nm were dispersed inside the carbonaceous matrix. Raman investigations revealed a high degree of amorphization of the carbonaceous matrix and showed hints for partial copper oxidation taking place selectively on the surfaces of the deposits. Optical transmission/reflection measurements of deposited pads showed a dielectric behavior of the material in the optical spectral range. The general behavior of the permittivity could be described by applying the Maxwell–Garnett mixing model to amorphous carbon and copper. The dielectric function measured from deposited pads was used to simulate the optical response of tip arrays fabricated out of the same precursor and showed good agreement with measurements. This paves the way for future plasmonic applications with copper-FEBID.

In this work, we have studied the synthesis of single crystalline self-catalyzed beta gallium oxide (β-Ga2O3) nanostructures by chemical vapor deposition technique. We have adopted a new approach to grow the nanostructures instead of using conventional foreign metal nano-catalyst based-approaches. The as-grown nanostructures including nanowires and nanosheets (NSHs) were grown on spin-coated Ga2O3 films. The structural studies such as X-ray diffraction, Raman and transmission electron microscope (TEM) investigations on the nanostructures showed monoclinic phase of Ga2O3 and single crystalline structure. Furthermore, high-resolution TEM with a selected area electron diffraction pattern recorded on a single β-Ga2O3 nanowire and nanosheet verified their single crystalline nature, having [001] as favorable growth direction. The energy dispersive X-ray spectroscopy-elemental mapping of as-grown nanostructures indicated uniform distribution of Ga and O. Cathodoluminescence imaging and spectrum revealed excellent luminescence characteristics of nanostructures with a broad UV-blue emission band (1.80–4.20 eV nm) centered at 2.64 eV. This study also highlights the growth mechanism of NSHs. These β-Ga2O3 nanostructures have great potential in nanofunctional devices.

Nanotextured surfaces provide an ideal platform for efficiently capturing and emitting light. However, the increased surface area in combination with surface defects induced by nanostructuring e.g. using reactive ion etching (RIE) negatively affects the device's active region and, thus, drastically decreases device performance. In this work, the influence of structural defects and surface states on the optical and electrical performance of InGaN/GaN nanorod (NR) light emitting diodes (LEDs) fabricated by top-down RIE of c-plane GaN with InGaN quantum wells was investigated. After proper surface treatment a significantly improved device performance could be shown. Therefore, wet chemical removal of damaged material in KOH solution followed by atomic layer deposition of only 10 [Formula: see text] alumina as wide bandgap oxide for passivation were successfully applied. Raman spectroscopy revealed that the initially compressively strained InGaN/GaN LED layer stack turned into a virtually completely relaxed GaN and partially relaxed InGaN combination after RIE etching of NRs. Time-correlated single photon counting provides evidence that both treatments-chemical etching and alumina deposition-reduce the number of pathways for non-radiative recombination. Steady-state photoluminescence revealed that the luminescent performance of the NR LEDs is increased by about 50% after KOH and 80% after additional alumina passivation. Finally, complete NR LED devices with a suspended graphene contact were fabricated, for which the effectiveness of the alumina passivation was successfully demonstrated by electroluminescence measurements.

Combining graphene with plasmonic nanostructures is currently being explored for high sensitivity biochemical detection based on the surface-enhanced Raman scattering (SERS) effect. Here, a novel and tunable platform for understanding SERS based on graphene monolayers transferred on arrays of split ring resonators (SRRs) exhibiting resonances in the visible range is introduced. Raman enhancement factors per area of graphene of up to 75 are measured, demonstrating the strong plasmonic coupling between graphene and the metamaterial resonances. Apart from the incident laser light, both the photoluminescence signal emitted by the SRRs and the Raman scattered light from graphene contribute to the excitation of distinct resonances, resulting in different SERS. This new perspective allows control of SERS in the case of graphene on plasmonic metamaterials or nanostructures and potentially paves the way towards an advanced SERS substrate that could lead to the detection of single molecules attached to graphene in future biochemical sensing devices.

The monolithic integration of wurtzite GaN on Si via metal-organic vapor phase epitaxy is strongly hampered by lattice and thermal mismatch as well as meltback etching. This study presents single-layer graphene as an atomically thin buffer layer for c-axis-oriented growth of vertically aligned GaN nanorods mediated by nanometer-sized AlGaN nucleation islands. Nanostructures of similar morphology are demonstrated on graphene-covered Si(111) as well as Si(100). High crystal and optical quality of the nanorods are evidenced through scanning transmission electron microscopy, micro-Raman, and cathodoluminescence measurements supported by finite-difference time-domain simulations. Current-voltage characteristics revealed high vertical conduction of the as-grown GaN nanorods through the Si substrates. These findings are substantial to advance the integration of GaN-based devices on any substrates of choice that sustains the GaN growth temperatures, thereby permitting novel designs of GaN-based heterojunction device concepts.

Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported.

Silicon nanowires (SiNWs) attached to a wafer substrate are converted to inversely tapered silicon nanocones (SiNCs). After excitation with visible light, individual SiNCs show a 200-fold enhanced integral band-to-band luminescence as compared to a straight SiNW reference. Furthermore, the reverse taper is responsible for multifold emission peaks in addition to the relatively broad near-infrared (NIR) luminescence spectrum. A thorough numerical mode analysis reveals that unlike a SiNW the inverted SiNC sustains a multitude of leaky whispering gallery modes. The modes are unique to this geometry and they are characterized by a relatively high quality factor (Q ~ 1300) and a low mode volume (0.2 eff)3 p ∝ Q/Vm of these modes can explain the enhanced luminescence in individual emission peaks as compared to the SiNW reference. Investigating the relation between the SiNC geometry and the mode formation leads to simple design rules that permit to control the number and wavelength of the hosted modes and therefore the luminescent emission peaks.

The study introduces a novel type of photonic structure, the inverted silicon nanocone (SiNC). It exhibits a unique photonic mode formation, and permits the design of novel silicon-based optoelectronic devices such as solar cells, light emitting diodes or optical sensors.

The successful integration of new, 3D nano-architectures into devices such as sensors, solarcells, light emitting diodes (LEDs) a.o. on a silicon (Si) platform requires new approaches towards fabrication and characterization. The present paper will show device concepts relying on Si nanowires (NWs) or inverted, cone-shaped, 1D Si structures (SiNCs) which permit the concentration and confinement of visible (VIS) and near infrared (NIR) light in whispering gallery modes (WGMs). Fabrication concepts based on nano-lithography and dry etching and optical property optimization based on numerical simulations (finite difference time domain - FDTD) will be presented. Individual as well as ensembles of these 1D nano-structures will be integrated in pn-junction solar cells (all-inorganic or organic-inorganic hybrids). Design rules for optimized absorption (VIS-NIR) will be derived. Moreover, novel carrier selective, nano-material composite based contacting schemes will be presented. Among those, silver nanowire based composites and graphene are demonstrated. Materials and device characterization will rely on advanced correlated electron microscopy and optical spectroscopy (CORMIC) containing electron beam induced current (EBIC) measurements, I-V characterization with and without illumination (with tunable power and wavelength) inside a scanning electron microscope (SEM), cathode-, photo- luminescence as well as in-SEM micro-Raman spectroscopy.

In the present paper, we study the influence of defects through their stress fields on the electrical activity and residual stress states of as-grown edge-defined film-feed (EFG) multicrystalline silicon (mc-Si) ribbons. We apply a combination of micro-Raman spectroscopy, electron beam induced current, defect etching and electron backscatter diffraction techniques that enables us to correlate internal stresses, recombination activity and microstructure on the micrometer scale. The stress fields of defect structures are considered to be too small (several tens of MPa) to influence directly the electrical activity, but they can enhance it via stress-induced accumulation of metallic impurities. It is commonly found that not all recombination-active dislocations on grain boundaries (GBs) and within grains are accompanied by internal stresses. The reason for this is that dislocations interact with each other and tend to locally rearrange in configurations of minimum strain energy in which their stress fields can cancel partially, totally or not at all. The outcome is a nonuniform distribution of electrical activity and internal stresses along the same GB, along different GBs of similar character as well as inside the same grain and inside different grains of similar crystallographic orientations. Our work has implications for developing crystal growth procedures that may lead to reduced internal stresses and consequently to improved electrical quality and mechanical stability of mc-Si materials by means of controlled interaction between structural defects.

Silicon nanowires (SiNWs) attached to a wafer substrate are converted to inversely tapered silicon nanocones (SiNCs). After excitation with visible light, individual SiNCs show a 200-fold enhanced integral band-to-band luminescence as compared to a straight SiNW reference. Furthermore, the reverse taper is responsible for multifold emission peaks in addition to the relatively broad near-infrared (NIR) luminescence spectrum. A thorough numerical mode analysis reveals that unlike a SiNW the inverted SiNC sustains a multitude of leaky whispering gallery modes. The modes are unique to this geometry and they are characterized by a relatively high quality factor (Q ~ 1300) and a low mode volume (0.2 eff)3 p ∝ Q/Vm of these modes can explain the enhanced luminescence in individual emission peaks as compared to the SiNW reference. Investigating the relation between the SiNC geometry and the mode formation leads to simple design rules that permit to control the number and wavelength of the hosted modes and therefore the luminescent emission peaks.

Nanoarchitectures for solar energy conversion are developed, characterized and integrated in device concepts. In particular thin film solar cells based on silicon nanostructures are proposed which have the potential for >15% efficiencies.

The scattering in the light emission wavelength of semiconductor nano-emitters assigned to nanoscale variations in strain, thickness, and composition is critical in current and novel nanotechnologies from highly efficient light sources to photovoltaics. Here, we present a correlated experimental and theoretical study of single nanorod light emitting diodes (nano-LEDs) based on InGaN/GaN multiquantum wells to separate the contributions of these intrinsic fluctuations. Cathodoluminescence measurements show that nano-LEDs with identical strain states probed by non-resonant micro-Raman spectroscopy can radiate light at different wavelengths. The deviations in the measured optical transitions agree very well with band profile calculations for quantum well thicknesses of 2.07-2.72 nm and In fractions of 17.5-19.5% tightly enclosing the growth values. The nanorod surface roughness controls the appearance of surface optical phonon modes with direct implications on the design of phonon assisted nano-LED devices. This work establishes a new, simple, and powerful methodology for fundamental understanding as well as quantitative analysis of the strain - light emission relationship and surface-related phenomena in the emerging field of nano-emitters.

The effect of ammonification temperature on the formation of coaxial GaN/Ga2O3 nanowires from β-Ga2O3 nanowires is reported in this work. High quality wurtzite GaN material showing a single c-plane phase is achieved from β-Ga2O3 nanowires having monoclinic crystal structure at a high ammonification temperature of 1050 °C. Lower ammonification temperatures such as 900 °C are also adequate for achieving coaxial GaN/Ga2O3 nanowire heterostructures, and the degree of GaN phase can be adjusted by varying the ammonification temperature. The crystalline quality of GaN/Ga2O3 nanowires improves with increasing the ammonification temperature. Resonant Raman spectra of GaN/Ga2O3 nanowires show Raman progression through multiple longitudinal-optical-phonon modes with overtones of up to second order. The development and improvement of the emission peak toward the near band edge of GaN at different ammonification temperatures were investigated using cathodoluminescence and photoluminescence characterization.

Osteocytes-the central regulators of bone remodeling-are enclosed in a network of microcavities (lacunae) and nanocanals (canaliculi) pervading the mineralized bone. In a hitherto obscure process related to aging and disease, local plugs in the lacuno-canalicular network disrupt cellular communication and impede bone homeostasis. By utilizing a suite of high-resolution imaging and physics-based techniques, it is shown here that the local plugs develop by accumulation and fusion of calcified nanospherites in lacunae and canaliculi (micropetrosis). Two distinctive nanospherites phenotypes are found to originate from different osteocytic elements. A substantial deviation in the spherites' composition in comparison to mineralized bone further suggests a mineralization process unlike regular bone mineralization. Clearly, mineralization of osteocyte lacunae qualifies as a strong marker for degrading bone material quality in skeletal aging. The understanding of micropetrosis may guide future therapeutics toward preserving osteocyte viability to maintain mechanical competence and fracture resistance of bone in elderly individuals.

Micro-Raman spectroscopy is a method that has been used since the 1960s in solid state physics to investigate orientation of crystals, mechanical stresses, phase changes as well as dopant concentrations in semiconductor materials. Raman spectroscopy measures these effects in crystals via an inelastic interaction of laser light with lattice vibrations. The method probes the material of interest nondestructively without requiring any complex sample preparations. Another beneficial aspect of Micro-Raman spectroscopy is that, compared to many other methods, no expensive vacuum equipment is needed for the measurements.

We see a real potential of the SIS SiNW based thin film cell on glass for further improvement of cell parameters such as Voc to 600-700 mV and a power conversation efficiency of >15%.

Macro-Raman spectroscopy is a technique that permits fast large area Raman analysis of materials. The fast collection of Raman signals is based on scanning the standard laser micro-spot across the sample by two orthogonally rotating piezo-mirrors resulting in a probing macro-spot the size of which is limited only by the opening of the used microscope objective. In the present paper, we show the instrument capabilities of the Macro-Raman spectrometer with respect to the statistical characterization of internal stresses (quantitatively), defect densities (qualitatively) and their correlation in multi-crystalline silicon (mc-Si) thin film solar cells on glass. While the lateral resolution decreases, the spectral information is preserved when integrating the Raman signal over increasingly large macro-spot sizes. The Macro-Raman results have been successfully used for the optimization of technological processes towards the lowest internal stresses and defect densities in thin film silicon solar cell materials. Our study demonstrates that Macro-Raman spectroscopy represents an advanced investigation method that can be applied both in a laboratory and factory environment for materials quality control.

Internal stresses in multi-crystalline silicon (mc-Si) materials for solar cells are the result of the superposition between the thermally induced residual stresses and the defect-related stresses. In the present contribution, we attempt to clarify the influence of internal stresses on the electrical activity of extended structural defects in edge-defined film-feed (EFG) ribbons and block-cast mc-Si wafers. For this purpose, we apply at identical positions a combination of micro-Raman, electron beam induced current (EBIC), defect etching, and electron backscatter diffraction (EBSD) techniques. Since the materials are cut into wafers and then into small pieces, the thermally induced residual stresses relax to a large extent by the creation of free surfaces. Thus, the measured internal stresses are mainly produced by defects. These stresses are too small (several tens of MPa) to influence directly the electrical activity, but they can enhance it via stress-induced accumulation of metallic impurities at defects.

We introduce and demonstrate two innovative macro-Raman mapping modes for advanced microstructural and mechanical characterization of photovoltaic (PV) materials. The macro- and micro- Raman results presented in this work are obtained on multicrystalline silicon (mc-Si) thin films on glass for solar cells. We show that detailed information can be extracted from the same first-order Raman spectra of solar silicon. This enables us to understand the interaction between stresses, defects, doping/impurities, and microstructure at identical positions as well as at different length scales. The fast and large-scale imaging Raman instrument allows us to evaluate statistically the materials properties and to see clearly the differences originating from different preparation conditions/processing. Based on these results, we believe that the Raman technique will become increasingly important in the PV community not only for fundamental studies but also for optimization and in-line quality check in a PV factory.

We report research on the characterization of stresses in relation to defects in multicrystalline silicon (mc-Si) solar cell material. Photoelasticity and micro-Raman spectroscopy (μRS) techniques are combined to understand this correlation at different length scales. While photoelasticity can probe small residual thermal stresses distributed over the entire volume of the sample as well as local stresses caused by defects, μRS can measure very localized intrinsic stresses of defects existing at the sample surface. Defects such as dislocations and inclusions are usually accompanied by stresses. In combination with thermal stresses, it results in a global residual stress state in the material. Thermal stresses are induced by the mismatch of different coefficients of thermal expansion between inclusions and silicon as well as due to local inhomogeneous temperature gradients during crystallization. Thermal stresses that relax by forming efficiency limiting defects can be reduced below the yield stress values by optimizing the crystallization conditions using photoelasticity.

Micro-Raman spectroscopy is used to measure stress distributions in 1.5 µm thick polycrystalline silicon thin film solar cells on glass. These measurements are combined with transmission electron microscopy and atomic force microscopy to assign the measured local stresses to the sample's microstructure. Expansion and contraction of the silicon lattice in the layer and the borosilicate glass substrate during the thermal processing of the solar cell as well as quartz beads of µm size that reside on the glass substrate for light-trapping purposes induce internal stresses that locally vary with structural features. While the thermal processing induces an average tensile stress in the silicon layer originating from the thermal mismatch between glass and silicon, the latter results in lateral stress gradients up to 208 ± 12 MPa in the mapped area.

Transparent conductive thin films are a key building block of modern optoelectronic devices. A promising alternative to expensive indium containing oxides is aluminum doped zinc oxide (AZO). By correlating spectroscopic ellipsometry and photoluminescence, we analyzed the contributions of different optical transitions in AZO grown by atomic layer deposition to a model dielectric function (MDF) over a wide range of photon energies. The derived MDF reflects the effects of the actual band structure and therefore describes the optical properties very accurately. The presented MDF is solely based on physically meaningful parameters in contrast to empirical models like e.g. the widely used Sellmeier equation, but nevertheless real and imaginary parts are expressed as closed-form expressions. We analyzed the influence of the position of the Fermi energy and the Fermi-edge singularity to the different parts of the MDF. This information is relevant for design and simulation of optoelectronic devices and can be determined by analyzing the results from spectroscopic ellipsometry.

New materials with high dielectric constant are currently being explored to replace silicon dioxide as gate dielectric for device scaling below 0.1 μm. With respect to conventional SiO2, these high permittivity dielectrics provide the required equivalent oxide thickness (EOT) without of further reduction of the insulator physical thickness, which is a key issue to limit gate leakage current and to maintain comparable MOSFET operation and reliability. The present paper presents preliminary results on conduction mechanisms in thin epitaxial SrTiO3 films grown by MBE on Si (100). I-V measurements were performed on Al/STO/Si structures at temperatures ranging from 40 K to 290 K. At temperatures lower than 100 K the conduction mechanism of electrons from gate electrode across the oxide barrier neither Schottky emission nor tunneling. For temperatures higher than 100 K Schottky emission occurs and barrier heights were extracted, showing an approximate linearly increase with temperature. In case of Si/STO interface, a Fowler-Nordheim tunneling mechanism was detected at 40 K and at intermediate fields. The extracted barrier heights are: 0.07 eV at Si/STO interface and from 0.26 eV (130 K) to 0.53 eV (290 K) at Al/STO interface.

In this paper, we demonstrate a new catalyst (Fe) to grow single crystalline beta-gallium oxide (?-Ga2O3) nanowires (NWs) via the vapour?liquid?solid mechanism using the chemical vapour deposition technique. The structural studies of these NWs showed the highly crystalline monoclinic phase of Ga2O3. This was confirmed by detailed scanning transmission electron microscope investigations demonstrating the NW to be single crystalline ?-Ga2O3, growing along the normal of the plane. We also compared Raman and cathodoluminescence (CL) properties of the as-grown ?-Ga2O3 NWs with a bulk Ga2O3 single crystal grown by the Czochralski method. It was observed that Raman peak positions of a single ?-Ga2O3 NW had a red frequency shift of about 0.3?1.4?cm?1 as compared to a bulk Ga2O3 single crystal, which was in fact quite small. In addition, the CL measurements of ?-Ga2O3 NWs and the bulk Ga2O3 single crystal exhibited similar spectra, having a strong broad UV?blue emission band and a weak red emission band. Moreover, the structural, morphological and optical properties of Fe-catalysed ?-Ga2O3 NWs were comparable to those of Au-catalysed ?-Ga2O3 NWs.

Self-assembled GaN rods were grown on sapphire by metal-organic vapor phase epitaxy using a simple two-step method that relies first on a nitridation step followed by GaN epitaxy. The mask-free rods formed without any additional catalyst. Most of the vertically aligned rods exhibit a regular hexagonal shape with sharp edges and smooth sidewall facets. Cathodo- and microphotoluminescence investigations were carried out on single GaN rods. Whispering gallery modes with quality factors greater than 4000 were measured demonstrating the high morphological and optical quality of the self-assembled GaN rods.

Simultaneous and locally resolved determination of the mechanical stress variation and the free hole concentration using Raman spectroscopy is demonstrated in laser crystallized amorphous silicon layers. Such layers are often used for the fabrication of thin film solar cells, e.g., on borosilicate glass substrates. The combined effects of stress and doping on the Raman signal can be separated based on the use of three wavelengths in the visible. The results show that the free hole concentration in the samples investigated varies between 1×1018 and 1.3×1019 cm−3. Stress as well as the free hole concentration vary substantially within the sample. The stress level varies between 575 and 850 MPa (±12 MPa). Cross-sectional transmission electron microscopy images show the presence of extended lattice defects such as dislocations and grain boundaries in the crystallized Si layer which could account for the lateral stress variations detected by Raman spectroscopy. The impact of film inhomogeneity in terms of stre...

Due to their large contact and loading surfaces as well as high sensitivities to chemical changes, graphene-based materials (GBMs) are increasingly being employed into novel nanomedicine technologies. Here biomolecule-monolayer graphene-kidney tissue hybrid structures are studied using mapping micro-Raman and fluorescence spectroscopies. Because in this configuration graphene interacts with molecules on both sides, a double-sided graphene-enhanced Raman scattering (GERS) effect up to ≈10.1 is found for biomolecules adsorbed on graphene and amino acids in the kidney tissue below graphene. Moreover, graphene causes an efficient autofluorescence quenching (FLQ) up to ≈20% emitted by the kidney tissue. Despite the complexity of such layered materials, the intriguing simultaneous occurrence of double-sided GERS (a new development of GERS) and FLQ phenomena can be well explained by suitable molecular structure and energy level alignment between molecules and graphene. These result in effective charge transfer mediated by non-covalent interactions as indicated by correlative strain, doping, and defect analyses in graphene based on the Raman data and energy level calculations. Last, the advantages of using graphene over standard photobleaching are demonstrated. This work can be extended to other macromolecular entities toward integrating GBMs in versatile drug delivery, imaging, and sensing devices.