Raman Peak Research Articles

Synthesis of high‑nitrogen-content doped-g-C3N4 (A new nitrogen source) diamond under high-pressure and high-temperature conditions

This study reports the successful synthesis of high‑nitrogen-content diamond (2723 ppm) within the Fe-Ni-C-N system, utilizing g-C3N4 as a new nitrogen source via the temperature gradient method under high-pressure and high-temperature (HTHP) conditions. The study investigated the role of nitrogen atoms in facilitating the growth of large diamonds with {111} plane orientation. Analysis of crystal morphology, nitrogen defect content, and nitrogen incorporation forms were conducted. As the amount of g-C3N4 increased, the crystal size decreased, the color changed from yellow to green with increasing depth, and the growth rate notably decreased. The Fourier transform microscopy infrared spectroscopy (FT-IR) characterization revealed increased nitrogen content within the crystal due to nitrogen atom introduction. Raman characterization indicated increased residual stress with higher nitrogen content, leading to shifts in Raman peak positions and broadening of half-peak widths of the diamond. Photoluminescence (PL) characterization indicated that g-C3N4 addition increased, resulting in a fading state of NV− and W8 defects. The results indicated that g-C3N4, as a new nitrogen source, exhibited superior doping efficiency within the diamond lattice compared with traditional nitrogen sources. The study offered valuable insights into the preparation and potential applications of high‑nitrogen diamond single crystals.

Dependence of the Raman vibration modes on structural properties of Tm:(ScxY1-x)2O3 laser ceramics with 0 ≤ x < 1.

We report on micro-Raman spectra of several mixed laser ceramics, i.e., 5at.%Tm:(ScxY1-xO2)3 with x = 0.121, 0.252, 0.489 and 5at.%Tm:Y2O3 ceramic. The samples were fabricated by solid-state pressureless consolidation of nanopowders produced by laser ablation of solid target in air flow. In particular, we studied the influence of Sc3+ content on the active vibration modes in terms of peak positions and shifts, linewidths and shapes: these parameters are relevant for the emission bandwidth of the laser medium. A shift towards higher frequencies is measured with the increase of the Sc3+ content in all samples in particular in (Tm0.048Y0.463Sc0.489O2)3 where the main Raman peaks are placed at 395, 494, 635 cm-1 while their shifts with Tm:Y2O3 are 22.6, 25.1, 40.1 cm-1, respectively. The assignment of the vibrational spectrum was obtained by density functional theory (DFT) with the Perdew-Burke-Enzerhof (PBE) exchange-correlation functional within the harmonic approximation framework.

Investigation of ion desolvation in aqueous electrolyte with carbon electrode via electrochemical in-situ Raman

Energy storage is an essential means to stabilize the fluctuation of renewable energy generation. Based on desolvation of electrolyte ions, high density charge storage in nanoporous electrodes has attracted widespread attention. The mechanism of ion transport within nanopores is currently under exploration. In this work, electric double layer capacitor was established using porous carbon electrode. Electrolytes with different hydrated/desolvatd ion radii were selected. The ion desolvation process was observed indirectly and concisely by using electrochemical in situ Raman technique on the carbon electrode. It was found that for ion with bigger solvation shells, its Raman intensity fluctuated with the cell charging voltage, which was caused by the desolvation of electrolyte ions. The desolvated ion has a strong polarization effect on the electron cloud of carbon. The influence of electrolyte concentrations on desolvation was also explored. High concentration electrolyte exhibits greater increase in Raman peak intensity. Our approach provides a way to study the physical mechanism and interface behavior of ion desolvation in electrochemical devices.

Rapid identification of living cancer cells based on label-free surface-enhanced Raman spectroscopy

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive vibration spectroscopy technique that can obtain fingerprint information of biomolecules in cells, and it has demonstrated significant potential in the early diagnosis of cancer. Here, we propose a rapid and efficient identification method of living cancer cells (within 10 min), which is based on the label-free SERS detection using iodide-modified Ag nanoparticles (Ag IMNPs) and the ultra-fast Raman mapping by line illumination. The Ag IMNPs achieve a better balance between sensitivity, reproducibility, and biocompatibility when compared to conventional Au or Ag nanoparticles. Statistical analysis of Raman peak frequency and intensity across substantial SERS spectra reveals a wealth of intracellular chemical information about the three cell lines 7701/7703/Caski. This method can not only accurately identify and classify normal cells, cancer cells, and various types of cancer cells, but it can also detect fingerprint changes in the distribution of intracellular chemicals. Furthermore, we discover that, among the three cell lines, liver cancer cells 7703 had the highest level of reactive oxygen species (ROS). This rapid SERS method can provide a new optical detection method for early screening, progression monitoring and prognosis assessment of tumors.

Quantum Chemical Investigation into the Structural Analysis and Calculated Raman Spectra of Amylose Modeled with Linked Glucose Molecules.

This study presents a quantum chemical investigation into the structural analysis and calculated Raman spectra of modeled amylose with varying units of linked glucose molecules. We systematically examined the rotation of hydroxymethyl groups and intramolecular hydrogen bonds within these amylose models. Our study found that as the number of linked glucose units increases, the linear structure becomes more complex, resulting in curled, cyclic, or helical structures facilitated by establishing various intramolecular interactions. The hydroxymethyl groups were confirmed to form interactions with oxygen atoms and with hydroxymethyl and hydroxyl groups from adjacent rings in the molecular structures. We identified distinct peaks and selected specific bands applicable in various analytical contexts by comparing their calculated Raman spectra. Representative vibrational modes within selected regions were identified across the different lengths of amylose models, serving as characteristic signatures for linear and more coiled structural conformations. Our findings contribute to a deeper understanding of amylose structures and spectroscopic signatures, with implications for theoretical studies and potential applications. This work provides valuable reference points for the detailed assignment of Raman peaks of amylose structure, facilitating their application in broader research on carbohydrate structures and their associated spectroscopic properties.

Simultaneous Protein Colorful Imaging via Raman Signal Classification.

Protein imaging aids diagnosis and drug development by revealing protein-drug interactions or protein levels. However, the challenges of imaging multiple proteins, reduced sensitivity, and high reliance on specific protein properties such as Raman peaks or refractive index hinder the understanding. Here, we introduce multiprotein colorful imaging through Raman signal classification. Our method utilized machine learning-assisted classification of Raman signals, which are the distinctive features of label-free proteins. As a result, three types of proteins could be imaged simultaneously. In addition, we could quantify individual proteins from a mixture of multiple proteins over a wide detection range (10 fg/mL-1 μg/mL). These results showed a 1000-fold improvement in sensitivity and a 30-fold increase in the upper limit of detection compared to existing methods. These advances will enhance our understanding of biology and facilitate the development of disease diagnoses and treatments.

Enhancing the stability of Sb2Se3 alloy through structural alterations on Bi addition

Sb2Se3 has attracted a lot of research interest as an environmentally friendly material with diverse applications. (Sb2Se3)100−xBix(x = 0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2) alloys are synthesized via melt quenching. Energy Dispersive X-ray (EDX) spectra confirm the Sb, Se, and Bi presence in bulk samples. X-ray diffraction (XRD) spectra confirm orthorhombic crystal structure in Bi-doped Sb2Se3 alloys. FTIR and Raman spectroscopy observations indicate an alteration in local structure on Bi addition. Far-IR spectroscopy points to Bi bonding with Se forming Bi2Se3 units. There is shifting of Raman peaks, corroborating the structural alteration in alloys on Bi incorporation. The peak intensity of Raman modes for Sb–Sb bond (B1g mode) decreases and for Sb–Se bond (A1g mode) increases, due to formation of Bi2Se3 structural units on Bi incorporation. The formation of stable Bi2Se3 units on Bi addition to Sb2Se3 alloys may be explored for potential application in topological insulators.

Advancing Insights into Runway De-Icing: Combining Infrared Thermography and Raman Spectroscopy to Assess Ice Melt

The “bare runway” principle aims to ensure passenger and employee safety by making runways more usable during winter conditions, allowing for easier removal of contaminants like snow and ice. Maintaining runway operations in winter is essential, but it involves considerable cost and environmental impacts. Greater knowledge about the de-icing and anti-icing performance of runway de-icing products (RDPs) optimizes operations. The ice melting test, as per the AS6170 standard, gauges the rate at which an RDP dissolves an ice mass to determine RDP effectiveness. Here, we introduce a novel integrated methodology for assessing RDP-related ice melting. We combine laboratory-based procedures with infrared thermography and Raman spectroscopy to monitor the condition of RDPs placed on ice. The plateau of maximum efficiency, marked by the most significant Raman peak intensity, corresponds to the peak minimum temperature, indicating optimal RDP performance. Beyond this point, RDP efficacy declines, and the system temperature, including melted contaminants and RDP, approaches ambient temperature. Effective RDP performance persists when the ambient temperature exceeds the mixture’s freezing point; otherwise, a freezing risk remains. The initial phases of RDP–ice contact involve exothermic reactions that generate brine, followed by heat exchange with surrounding ice to encourage melting. The final phase is complete ice melt, leaving only brine with reduced heat exchange on the surface. By quantifying these thermal and chemical changes, we gain a deeper understanding of RDP-related ice melting, and a more robust assessment can be provided to airports using RDPs.

Dynamic pressure-induced amorphous transition and crystallization behavior of 4-methylpyridine

The phase transitions of 4-methylpyridine (4MP) were studied under static pressure and dynamic pressure by in situ Raman spectroscopy. Under static compression, 4-methylpyridine underwent three phase transitions: a liquid to crystal I transition at 0.44 GPa; followed by transformation into crystal II at 2.17 GPa and crystal III at 10.36 GPa. Under dynamic compression, 4-methylpyridine was compressed into an amorphous phase as the pressure increased from 0.36, 0.38, and 0.33 GPa to 4.42, 6.80, and 11.53 GPa within 5 ms, respectively. Through the fitting of partial Raman peak linewidth with pressure, the compression rate has a significant effect on the disorder degree of crystal structure. During the pressure relief process, the amorphous 4-methylpyridine transformed into a new crystal Ⅰ’ at 2.40 GPa, and then returned to the initial liquid state at roughly 0.58 GPa. The phase transitions of 4-methylpyridine dynamic pressure can be explained by the faster compression rate that drives systems to break chemical equilibrium and generate a new phase.

Raman-based machine-learning platform reveals unique metabolic differences between IDHmut and IDHwt glioma.

Formalin-fixed, paraffin-embedded (FFPE) tissue slides are routinely used in cancer diagnosis, clinical decision-making, and stored in biobanks, but their utilization in Raman spectroscopy-based studies has been limited due to the background coming from embedding media. Spontaneous Raman spectroscopy was used for molecular fingerprinting of FFPE tissue from 46 patient samples with known methylation subtypes. Spectra were used to construct tumor/non-tumor, IDH1WT/IDH1mut, and methylation-subtype classifiers. Support vector machine and random forest were used to identify the most discriminatory Raman frequencies. Stimulated Raman spectroscopy was used to validate the frequencies identified. Mass spectrometry of glioma cell lines and TCGA were used to validate the biological findings. Here, we develop APOLLO (rAman-based PathOLogy of maLignant gliOma)-a computational workflow that predicts different subtypes of glioma from spontaneous Raman spectra of FFPE tissue slides. Our novel APOLLO platform distinguishes tumors from nontumor tissue and identifies novel Raman peaks corresponding to DNA and proteins that are more intense in the tumor. APOLLO differentiates isocitrate dehydrogenase 1 mutant (IDH1mut) from wild-type (IDH1WT) tumors and identifies cholesterol ester levels to be highly abundant in IDHmut glioma. Moreover, APOLLO achieves high discriminative power between finer, clinically relevant glioma methylation subtypes, distinguishing between the CpG island hypermethylated phenotype (G-CIMP)-high and G-CIMP-low molecular phenotypes within the IDH1mut types. Our results demonstrate the potential of label-free Raman spectroscopy to classify glioma subtypes from FFPE slides and to extract meaningful biological information thus opening the door for future applications on these archived tissues in other cancers.

The combined use of serum Raman spectroscopy and D dimer testing for the early diagnosis of acute aortic dissection

ObjectivesAcute aortic dissection (AAD) is an extremely life-threatening medical emergency, often misdiagnosed in its early stages, resulting in prolonged wait times for rescue. This study aims to identify potential serum biomarkers that can assist in the accurate diagnosis of AAD and effectively differentiate it from other conditions causing severe chest pain. MethodsA total of 122 patients with AAD and 129 patients with other severe chest pain disorders were included in the study. Serum samples were analyzed by measuring the peak intensities of Raman spectra. For each measurement, the Raman spectrum was accumulated by two accumulations (3 s per acquisition). Logistic regression and nomogram models were developed using these peak intensities as well as D-dimer levels to predict the occurrence of AAD. The clinical utilities of these models were assessed through receiver operating characteristics (ROC) curve analysis, net reclassification improvement (NRI), integrated discrimination improvement (IDI), and decision curve analysis (DCA) in both training and internal test cohorts. ResultsThe D-dimer levels of AAD patients were significantly increased, as well as higher intensities at specific Raman peaks, including 505 cm−1, 842 cm−1, 947 cm−1, 1254 cm−1, 1448 cm−1, and 1655 cm−1 when compared to non-AAD patients. Conversely, decreased intensities were observed at Raman peaks such as 750 cm−1, 1004 cm−1, 1153 cm−1, 1208 cm−1, and 1514 cm−1 in AAD patients. Least absolute shrinkage and selection operator regression analysis on the training cohort identified eight potential predictors: D-dimer along with intensity measurements at peaks such as 505 cm−1, 750 cm−1, 1153 cm−1, 1208 cm−1, 1254 cm−1, 1448 cm−1, and 1655 cm−1. The combination of these eight potential predictors demonstrated a good discriminatory performance, with an area under the curve (AUC) value of 0.928 in the training cohort and an AUC of 0.936 in the internal test cohort, outperforming the use of D-dimer alone. Furthermore, DCA curve analysis revealed that leveraging this combination of eight potential predictors would provide substantial net benefits for clinical application. Moreover, this combination significantly augmented discrimination power, as evidenced by a continuous NRI of 39.8 % and IDI of 9.95 % in the training cohort, as well as a continuous NRI of 27.1 % and IDI of 9.95 % in the internal test cohort. ConclusionsThe employment of this combination of eight potential predictors effectively rules out AAD to a greater extent. This study presents a promising diagnostic strategy for early detection using optical diagnostic techniques such as Raman spectroscopy.

Formation of macroscopic black dots in transparent alumina ceramics prepared by pulsed electric current sintering

Transparent alumina ceramics produced by pulsed electric current sintering (PECS) include black dots, which can be observed with the naked eye. These black dots have porous structures caused by the aggregates in the raw powder. In order to investigate the detailed mechanism of black dot formation, transparent alumina ceramics were prepared by sintering α-alumina granules to produce large pseudo-aggregates and introducing them into α-alumina powder for PECS. Macroscopic black dots were formed in the sample. Characteristic Raman peaks of graphite were detected in porous parts of these macroscopic black dots. Analysis of gas phases generated from graphite sheets for PECS suspected to be involved in carbon contamination showed CO and CO2 generation. In thermodynamic calculations on carbon activity during PECS, gas phase including CO and CO2 generated from the hot graphite mold/sheet permeates the porous part of the cold sample, and the carbon activity of gases including CO and CO2 on the porous surface theoretically exceeds unity. Then, CO is adsorbed and decomposed on the porous surface, resulting in carbon contamination. The formation of macroscopic black dots is caused by carbon deposition in agglomerates of the raw powder from CO generated by graphite sheets during PECS.

Adhesive-free bonding for hetero-integration of InP based coupons micro-transfer printed on SiO2 into Complementary Metal-Oxide-Semiconductor backend for Si photonics application on 8″ wafer platform

Micro-Transfer printing (µTP) is a promising technique for hetero-integration of III-V materials into Si-based photonic platforms. To enhance the print yield by increasing the adhesion between the III-V material and Si or SiO2 surface, an adhesion promoter like Benzocyclobutene is typically used as interlayer. In this work, we demonstrate µTP of InP based coupons on SiO2 interlayer without any adhesive interlayer and investigate the mechanism of adhesive free bonding. Source coupons are InP-based coupon stacks on a sacrificial layer that is removed by a chemical wet etch with FeCl3. For the target we fabricated amorphous-Si waveguides on 8″ wafer encapsulated by a High Density Plasma SiO2 which was planarized by a chemical mechanical polishing procedure. We used O2 plasma to activate both source and target to increase adhesion between coupon and substrate. To get a better understanding of the bonding mechanism we applied several surface characterization methods. Root mean square roughness of InP and SiO2 was measured by atomic force microscopy before and after plasma activation. The step height of the micro-transfer printed source coupon on the target wafer is estimated by optical step profiler. We used Raman peak position mappings of InP to analyze possible strain and contact angle measurements on SiO2, before and after plasma activation to observe a change in the hydrophilicity of the surface. X-ray Photoelectron Spectroscopy analysis was used to characterize the surface energy states of P2p, In3d, O1s for InP source and Si2p, O1s for SiO2 target. Our results demonstrate direct bonding of InP coupons by means of µTP without the need of a strain-compensation layer. In this way, a promising route towards Complementary Metal-Oxide-Semiconductor compatible use of µTP for the hetero-integration of InP is provided.

Are Selenides the Same as Sulfides? Structure, Spectroscopy, and Properties of Narrow-Gap Rare-Earth Semiconductors RE2Sn(S1-xSex)5 (RE = La, Ce; x = 0-0.8).

The ternary rare-earth sulfides RE2SnS5 (RE = La-Nd) and the partial solid solutions RE2Sn(S1-xSex)5 (RE = La, Ce; x = 0-0.8) were prepared in the form of polycrystalline samples by reaction of the elements at 900 °C and as single crystals in the presence of KBr flux. They adopt the La2SnS5-type structure (orthorhombic, space group Pbam, Z = 2) consisting of chains of edge-sharing SnCh6 octahedra separated by RE atoms. Although the cell parameters evolve smoothly in RE2Sn(S1-xSex)5, detailed structural analysis by single-crystal X-ray diffraction revealed a pronounced preference for the Se atoms to occupy two out of the three chalcogen sites, which offers a rationalization for why the all-selenide end-members RE2SnSe5 do not form. Solid-state 119Sn NMR spectra confirmed the nonrandom distribution of SnS6-nSen local environments, which could be resolved into individual resonances. The Raman spectra of RE2SnS5 compounds show an intense peak at 307-320 cm-1 assigned to a symmetric A1g mode, which is dominated by Sn-S bonds; the Raman peak intensities varied with Se substitution in La2Sn(S1-xSex)5. Optical diffuse reflectance spectra, band structure calculations, and electrochemical impedance spectra indicated that these compounds are narrow band gap semiconductors; the optical band gaps are insensitive to RE substitution in RE2SnS5 (0.7 eV) but they gradually decrease with greater Se substitution in RE2Sn(S1-xSex)5 (0.7-0.4 eV).

Discriminating between diabetic and non-diabetic patient’s blood serum using near-infrared Raman spectroscopy

The current study demonstrates the utilization of Raman spectroscopy, employing a laser system emitting @ 785 nm, and multivariate analysis for the accurate assessment of diabetes (glucose) in human blood sera. Raman spectra of sera samples collected from 40 patients of both genders of different age groups were acquired in the spectral range of 600–1800 cm−1. For comparison, the Raman spectra of non-diabetic healthy individuals were also obtained in the same spectral range. Apparent variations were found in normal and pathological samples at peak positions of 700 cm−1, 750 cm−1, 879 cm−1, 950 cm−1, band at 1004 cm−1 to 1006 cm−1, 1048 cm−1, 1060 cm−1, 1082 cm−1, 1091 cm−1, 1170 cm−1, 1247 cm−1, 1330 cm−1, 1333 cm−1, 1367 cm−1, 1659 cm−1 and 1745 cm−1. These variations are most likely due to variations in the concentration of amino-acid methionine, glycosylated, tryptophan, polysaccharides, phenylalanine, glycogen, glucose, carbohydrates, carbohydrates (C–O–H), tyrosine, guanine, typical phospholipids, guanine, phospholipid, cholesterol band, and triglycerides (fatty acids) respectively. For highlighting the spectral differences between the two data sets principal component analysis was used. The observed variations in Raman peaks provide an in-depth biochemical fingerprint of the samples and can be used as a biomarker for medical diagnosis effectively at the mass level.

Evidences for local non-centrosymmetricity and strong phonon anomaly in EuCu2As2: a Raman spectroscopy and lattice dynamics study

Phonon modes and their association with the electronic states have been investigated for the metallic EuCu2As2 system. In this work, we present the Raman spectra of this pnictide system which clearly shows the presence of seven well defined peaks above 100 cm−1 that is consistent with the locally non-centrosymmetric P4/nmm crystal structure, contrary to that what is expected from the accepted symmorphic I4/mmm structure. Lattice dynamics calculations using the P4/nmm symmetry attest that there is a commendable agreement between the calculated phonon spectra at the Γ point and the observed Raman mode frequencies, with the most intense peak at ∼232 cm−1 being ascribed to the A 1g mode. Temperature dependent Raman measurements show that there is a significant deviation from the expected anharmonic behaviour around 165 K for the A 1g mode, with anomalies being observed for several other modes as well, although to a lesser extent. Attempts are made to rationalize the observed anomalous behavior related to the hardening of the phonon modes, with parallels being drawn from metal dichalcogenide and allied systems. Similarities in the evolution of the Raman peak frequencies with temperature seem to suggest a strong signature of a subtle electronic density wave instability below 165 K in this compound.

Microstructure and optical properties of ZnAlO films prepared by Magnetron sputtering

ZnAlO thin films with different Al concentrations were prepared on glass and silicon substrates by Magnetron sputtering in this paper. Scanning electron microscopy (SEM), X-ray diffraction (XRD), spectrometer and other instruments were used to analyze the surface morphology, microstructure, transmittance and Raman spectrum of the films. The results showed that trace Al doping significantly increased the surface morphology and size of ZnAlO thin films; The low doped ZnAlO thin film exhibits a good preferred orientation. As the Al doping concentration increases, the main growth direction of the crystal gradually shifts from (101) to (103), and the grain size decreases with the increase of doping concentration during low doping; When the wavelength of ZnAlO film is less than 330 nm, the transmittance of the film is almost zero; When the wavelength is greater than 350 nm, the transmittance of the thin film decreases with the increase of Al doping concentration, and there is a blue shift trend with the increase of Al concentration. When the wavelength is between 420-900nm, the average transmittance of ZnAlO thin film can reach over 90%, and the transmission performance is good; The ZnAlO thin films all have structural characteristic peaks of wurtzite with a frequency of about 437 cm−1, and the Raman peak position does not move with the increase of Al concentration.

Denoising and Baseline Correction Methods for Raman Spectroscopy Based on Convolutional Autoencoder: A Unified Solution.

Preprocessing plays a key role in Raman spectral analysis. However, classical preprocessing algorithms often have issues with reducing Raman peak intensities and changing the peak shape when processing spectra. This paper introduces a unified solution for preprocessing based on a convolutional autoencoder to enhance Raman spectroscopy data. One is a denoising algorithm that uses a convolutional denoising autoencoder (CDAE model), and the other is a baseline correction algorithm based on a convolutional autoencoder (CAE+ model). The CDAE model incorporates two additional convolutional layers in its bottleneck layer for enhanced noise reduction. The CAE+ model not only adds convolutional layers at the bottleneck but also includes a comparison function after the decoding for effective baseline correction. The proposed models were validated using both simulated spectra and experimental spectra measured with a Raman spectrometer system. Comparing their performance with that of traditional signal processing techniques, the results of the CDAE-CAE+ model show improvements in noise reduction and Raman peak preservation.

Assessing the Stress Induced by Novel Packaging in GaN HEMT Devices via Raman Spectroscopy

Micro-Raman spectroscopy was carried out to evaluate the localized residual stresses in commercial Gallium-Nitride-based devices, specifically, AlGaN/GaN high-electron-mobility Transistors (HEMTs) with a novel packaging design provided by STMicroelectronics S.r.l. (Catania, Italy). The packaging plays a key role in protecting the device core against the external environment, thus minimizing damages caused by mechanical shocks, exposure to light, and contact with chemicals, conjointly achieving an efficient heat dissipation rate. Even though the packaging is a required step for the proper functioning of ready-to-use electronic devices, its application typically may introduce mechanical stress to AlGaN/GaN HEMTs, which can result in various reliability issues. In this paper, we investigate the impact of packaging on residual stress by analyzing the frequency shift of the E2 Raman peak along GaN layers and at the GaN/Si interface. An extensive evaluation was conducted using both a packaged device and a wafer-level device. The correlation between Raman frequency shifts of the E2 mode was accurately quantified, revealing a stress mitigation of approximately 0.1 GPa. This reduction is ascribed to the compressive stress introduced by the packaging, which partially offsets the intrinsic tensile stress of the wafer-level device. The proposed methodology could, in principle, be implemented to improve the development of packaging.

Raman peak shift and broadening in crystalline nanoparticles with lattice impurities

The effect of point-like lattice impurities on nanoparticle Raman spectra is studied using both numerical and analytical methods. Particular cases of replacement atoms of various masses, vacancies, and disorder in interatomic bonds are considered. It is shown that the disorder leads not only to the broadening of optical phonon lines but also to the shift of the corresponding Raman peak. The latter can be either positive (i.e., blueshift) or negative (redshift) depending on the type of impurities. Thus there is an additional contribution to the well-known redshift that occurs due to the size-quantization (confinement) effect. Considering nanometer-sized diamond particles as a representative example, we show that the broadening and the shift are, as a rule, of the same order of magnitude. The results are discussed in the framework of the self-consistent T-matrix approach. It is argued that both effects should be considered for accurate treatment of experimental Raman spectra. Simple recipes to do so are formulated for several important cases including NV centers in nanodiamonds.