Electronic States Research Articles

PyCTRAMER: A Python package for charge transfer rate constant of condensed-phase systems from Marcus theory to Fermi's golden rule.

In this work, we introduce PyCTRAMER, a comprehensive Python package designed for calculating charge transfer (CT) rate constants in disordered condensed-phase systems at finite temperatures, such as organic photovoltaic (OPV) materials. PyCTRAMER is a restructured and enriched version of the CTRAMER (Charge-Transfer RAtes from Molecular dynamics, Electronic structure, and Rate theory) package [Tinnin et al. J. Chem. Phys. 154, 214108 (2021)], enabling the computation of the Marcus CT rate constant and the six levels of the linearized semiclassical approximations of Fermi's golden rule (FGR) rate constant. It supports various types of intramolecular and intermolecular CT transitions from the excitonic states to CT state. Integrating quantum chemistry calculations, all-atom molecular dynamics (MD) simulations, spin-boson model construction, and rate constant calculations, PyCTRAMER offers an automatic workflow for handling photoinduced CT processes in explicit solvent environments and interfacial CT in amorphous donor/acceptor blends. The package also provides versatile tools for individual workflow steps, including electronic state analysis, state-specific force field construction, MD simulations, and spin-boson model construction from energy trajectories. We demonstrate the software's capabilities through two examples, highlighting both intramolecular and intermolecular CT processes in prototypical OPV systems.

Exploring Excited State Landscapes with Surface Enhanced Hyper-Raman Spectroscopy.

In this Perspective, we provide a historical overview of the surface-enhanced hyper-Raman scattering (SEHRS) effect, describe its essential components, highlight the close connection between theory and experiment in several vignettes, and discuss recent analytical applications. SEHRS, the two-photon analog of surface-enhanced Raman scattering (SERS), is a spontaneous nonlinear scattering exhibited by molecules in a plasmonic field. Hyper Raman provides distinctive information on the molecular vibrations and electronic excited states of analytes. A 40-year old mystery surrounding the SEHRS spectra of R6G is used to illustrate the power of SEHRS to explore excited electronic states, revealing how non-Condon effects can influence the two-photon molecular properties. The exceptionally large enhancement factors (>1013) obtained from SEHRS enable the analysis of single molecules and molecules at very low concentrations. This high sensitivity is further augmented by an increased sensitivity to chemical effects, allowing SEHRS to probe changes in the local environment and the orientation of surface ligands. As most SEHRS experiments employ near-infrared (NIR) and short-wave infrared (SWIR) light, it also holds promise for bioimaging studies. Before concluding, we discuss future directions and challenges for the field as it moves forward.

The vibrational spectra of a model boron dipyrromethene molecule in condensed phase: Experimental and theoretical insights

Boron dipyrromethene (BODIPY) derivatives are an important class of organic molecular dyes. Their chemical structure can be easily modified by synthetic methods, introducing various substituent groups on a tricyclic core that represents the characteristic unit of these compounds. As a consequence, BODIPY optical properties can be designed to tune their absorption and emission in an especially wide wavelength range. A large amount of experimental and computational studies has been performed to investigate the electronic excited states of many structurally different BODIPY dyes. On the other hand, vibrational properties are by far less known for these compounds. We have therefore measured detailed infrared and Raman spectra of a model compound, namely, a BODIPY derivative with four methyl groups and a phenyl ring as substituents. The experimental spectra of the solid sample have been contrasted with ab initio spectra computed at the CAM-B3LYP/6-31G+(d) level. Computations have been performed both for the isolated molecule and including the crystalline environment. In the latter case, better agreement has been observed. An assignment is proposed for the 123 vibrational modes. These results form the basis for further spectroscopic studies on complex BODIPY derivatives.

Electronic and optical properties of all-inorganic TiX3 transition metal halide nanowires

Transition metal halides are promising for use in photovoltaics and optoelectronics. This research systematically investigated the composition-dependent electronic and optical properties of all-inorganic TiX3 (X = Cl/Br/I) transition metal halide nanowires using first-principles density functional theory (DFT) and time-dependent DFT calculations. The findings emphasize the significant impact of the specific halide type on the electronic and optical characteristics of TiX3 nanowires. Particularly, the type of halide significantly influences the electronic states near the Fermi level and the infrared photoabsorption properties. An important discovery is the exceptional photoabsorption strength observed in the TiCl3 nanowire, reaching an impressive value of 26000 cm−1. The study also offers insights into exciton generation, aided by Transition Contribution Maps. Apart from its theoretical implications, we expect that the insights gained from this research will contribute to the advancement of active optical devices utilizing all-inorganic halide perovskites.

Boosting the Electrochemical Oxygen Evolution with Nickel Oxide Nanoparticle-Modified Glassy Carbon Electrodes in Alkaline Solutions.

The present work investigates the electrocatalysis of oxygen evolution (OE) on a glassy carbon electrode modified with nickel oxide nanoparticles (NPs) (nano-Ni) in an alkaline solution. The nano-Ni is electrodeposited from an acidic sulfate electrolyte containing various additives, such as glucose, glycerol, and dimethyl glyoxime. The NPs are characterized morphologically and electrochemically using scanning electron microscopy and cyclic voltammetry. The elemental composition and electronic state of the modified electrodes were analyzed using X-ray photoelectron spectroscopy. A considerable enhancement in electrocatalytic activity, depending on the additives used, is observed. The study also explores the effect of nickel oxide loading to optimize the process. The highest cathodic shift in the onset potential of the oxygen evolution reaction is achieved with nickel oxide deposited in the presence of ethylene glycol.

Topology Control of Covalent Organic Frameworks with Interlaced Unsaturated 2D and Saturated 3D Units for Boosting Electrocatalytic Hydrogen Peroxide Production.

Modulating the electronic state of multicomponent covalent organic framework (COF) electrocatalysts is crucial for enhancing catalytic activity. However, the effect of dimensionality on their physicochemical functionalities is still lacking. Herein, we report an interlaced unsaturated 2D and saturated 3D strategy to develop multicomponent-regulated COFs with tunable gradient dimensionality for high selectivity and activity electrocatalysis. Compared with the two-component 2D and 3D model COFs, the 2D/3D framework interlaced COFs with locally irregular dimensions and electronic structures are more practical in optimizing the intrinsic electrode surface reaction and mass transfer. Remarkably, the unsaturated 2D-inserted 3D TAE-COF regulates the adsorption mode of OOH* species to supply a favorable dynamic pathway for the H2O2 process, thereby achieving an excellent production rate of 8.50 mol gcat -1 h-1. Moreover, utilizing theoretical calculation and in situ ATR-FTIR experiment, we found that the central carbon atom of the tetraphenyl-based unit (site-1 and site-6) are potential active sites. This strategy of operating the adsorption ability of reactants with dimensionality-interconnected building blocks provides an idea for designing durable and efficient electrocatalysts.

Topology Control of Covalent Organic Frameworks with Interlaced Unsaturated 2D and Saturated 3D Units for Boosting Electrocatalytic Hydrogen Peroxide Production

AbstractModulating the electronic state of multicomponent covalent organic framework (COF) electrocatalysts is crucial for enhancing catalytic activity. However, the effect of dimensionality on their physicochemical functionalities is still lacking. Herein, we report an interlaced unsaturated 2D and saturated 3D strategy to develop multicomponent‐regulated COFs with tunable gradient dimensionality for high selectivity and activity electrocatalysis. Compared with the two‐component 2D and 3D model COFs, the 2D/3D framework interlaced COFs with locally irregular dimensions and electronic structures are more practical in optimizing the intrinsic electrode surface reaction and mass transfer. Remarkably, the unsaturated 2D‐inserted 3D TAE‐COF regulates the adsorption mode of OOH* species to supply a favorable dynamic pathway for the H2O2 process, thereby achieving an excellent production rate of 8.50 mol gcat−1 h−1. Moreover, utilizing theoretical calculation and in situ ATR‐FTIR experiment, we found that the central carbon atom of the tetraphenyl‐based unit (site‐1 and site‐6) are potential active sites. This strategy of operating the adsorption ability of reactants with dimensionality‐interconnected building blocks provides an idea for designing durable and efficient electrocatalysts.

Making Peace with Random Phases: Ab Initio Conical Intersection Quantum Dynamics in Random Gauges.

Ab initio modeling of conical intersection wave packet dynamics is crucial for various photochemical, photophysical, and biological processes. However, adiabatic electronic states obtained from electronic structure computations involve random phases, or more generally, random gauge fixings, which cannot be directly used in the modeling of nonadiabatic wave packet simulations. Here we develop a random-gauge local diabatic representation that allows an exact modeling of conical intersection dynamics directly using the adiabatic electronic states with phases randomly assigned during the electronic structure computations. Its utility is demonstrated by an exact ab initio modeling of the two-dimensional Shin-Metiu model with and without an external magnetic field. Our results provide a simple approach to integrating the electronic structure computations into nonadiabatic quantum dynamics, thus paving the way for ab initio modeling of conical intersection dynamics.

Evidence as conformational molecular switch of 1,4-bis(4-vinylpyridyl)benzene adsorbed on a nanostructured silver surface: A synergetic study of femtosecond transient absorption spectra, electrochemical SERS records and DFT calculations

The electrochemical surface-enhanced Raman spectra (SERS) of 1,4-bis(4-vinylpyridyl)benzene (bvpb) recorded at different electrode potentials with three excitation wavelengths (785, 532 and 473 nm) point out there exists a resonance process involved at more negative voltage with the 785 nm line, giving two strongly enhanced SERS bands at about 1500 and 1150 cm−1. This result agrees with the VIS-NIR transient absorption spectrum characterized by a strong band at 607 nm and a weaker one at 1163 nm, corresponding to the first singlet (S1) and triplet (T1) excited electronic states. The DFT potential energy curve corresponding to the trans–cis (E-Z) isomerization in the S0 state and in the two lowest S1 and T1 excited states, indicates that the S1 state exhibits a significant lower barrier height than S0 state, showing also a S1/S0 conical intersection at a structural conformation in which the vinyl double bond twists by 90°. TD-DFT resonance Raman spectra of the planar and twisted conformation in a simple model of surface complex, Ag20-bvpb, yield that the twisted molecule is able to predict the selected enhancement of the two SERS bands. Therefore, bvpb could act as an electroactive conformational molecular switch under a selected wavelength in nanoelectronic devices.

Bose–Einstein condensation of light in a semiconductor quantum well microcavity

When particles with integer spin accumulate at low temperature and high density, they undergo Bose–Einstein condensation (BEC). Atoms, magnons, solid-state excitons, surface plasmon polaritons and excitons coupled to light exhibit BEC, which results in high coherence due to massive occupation of the respective system’s ground state. Surprisingly, photons were shown to exhibit BEC recently in organic-dye-filled optical microcavities, which—owing to the photon’s low mass—occurs at room temperature. Here we demonstrate that photons within an inorganic semiconductor microcavity also thermalize and undergo BEC. Although semiconductor lasers are understood to operate out of thermal equilibrium, we identify a region of good thermalization in our system where we can clearly distinguish laser action from BEC. Semiconductor microcavities are a robust system for exploring the physics and applications of quantum statistical photon condensates. In practical terms, photon BECs offer their critical behaviour at lower thresholds than lasers. Our study shows two further advantages: the lack of dark electronic states in inorganic semiconductors allows these BECs to be sustained continuously; and quantum wells offer stronger photon–photon scattering. We measure an unoptimized interaction parameter (g̃\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ilde{{{{{g}}}}}$$\\end{document} ≳ 10–3), which is large enough to access the rich physics of interactions within BECs, such as superfluid light.

Missing-cell defects in QCA wires: The ground and excited electronic states perspectives

Quantum Cellular Automata (QCA) technology offers promising prospects for designing molecular electronic circuits that operate at high frequencies and with ultra-low power consumption. QCA wires serve as crucial conduits for digital data transmission between logic gates. A series of QCA cells arranged sequentially forms these wires, with data written or read using paired nanogap electrodes. In this study, employing a simplified full-basis quantum mechanical model, we investigate the impact of single and double missing cells on the response function and output voltage of wires implemented within the two-dot QCA architecture. The electronic coupling between the quantum dots within each QCA cell stands out as a critical structural parameter influencing both the nonlinearity of the response function and the level of output voltage. Ground state analyses of wires affected by missing-cell defects suggest that employing QCA cells with weak electronic coupling could potentially enhance fault tolerance. However, examination of excited states reveals that reducing electronic coupling may compromise the thermal robustness of such defective QCA wires.

Rovibrational Line Lists of Triplet and Singlet Methylene.

The methylene molecule (CH2) is a short-lived radical with lacking data on its spectral line intensities. Although the lifetime of CH2 is extremely short under Earth's conditions, it exists in a free form in interstellar media. CH2 is an important intermediate species in chemical reactions associated with the formation and destruction of complex hydrocarbons. We present the first rovibrational line lists of CH2 in its ground triplet and first excited singlet electronic state. To this end, our previously developed accurate ab initio potential energy surface (PES) was used for the ground electronic triplet state [Egorov et al. J. Comp. Chem. 2024. V. 45. (2). P. 83] while a new PES for the singlet state was constructed in this work using the single-reference coupled cluster approach [CCSD(T)] combined with the extrapolation to the complete basis set (CBS) limit based on the correlation-consistent orbital basis sets with the core-valence electron correlation effects [aug-cc-pCVXZ, X = T, Q, 5, and 6]. In addition, the contributions to the correlation energy from highly excited Slater determinants [CC(n), n = 3-5] were included as well as the scalar relativistic effects and DBOC. The most accurate description of the infrared band origins of singlet CH2 was thus achieved for the energy range where the impact of the nonadiabatic coupling due to the Renner-Teller effect can be neglected. To obtain the probabilities of the rovibrational transitions, new ab initio DMSs were constructed both for the triplet and singlet CH2 using the CCSD(T)/aug-cc-pCVQZ approach. Finally, the absorption spectra of triplet and singlet methylene were predicted from the variationally computed line lists.

(Invited) Predicting the Optical Spectra of Fullerenes with Vibronic Coupling

Following the mid-1980s discovery of fullerenes, their optical properties quickly drew a lot of attention as the intrinsically allowed electronic transitions did not seem to alone explain the complexities of their spectra. Even after more than three decades, there is still little knowledge of the intricate details of their absorption and emission spectra. The main issue with these carbon cages is the high density of electronic states in the energy range of interest. From an experimental standpoint, this means that high resolution spectra are needed to accurately distinguish the electronic and vibronic structure. On the other hand, such a high density of electronic states tests the limits of first-principle calculations, as the computational cost for precisely predicting electronic states quickly becomes prohibitive for systems as large as fullerenes.In this presentation, we will discuss the challenges and importance of including vibronic coupling in the Ab initio calculation of fullerenes' optical spectra. This is necessary in order to gain a reliable interpretation of their electronic spectra and make the most of spectroscopy to probe the electronic structure of fullerenes.

(Invited) Sulfur Addition Reaction Onto Carbon Nanotubes

The surface chemistry of carbon nanotubes is of interest for material’s processing and modification of their electronic and optical properties. Here, we present a new sulfur addition reaction to single-wall and multi-wall carbon nanotubes. Depending on the reaction conditions, we find strong evidence of addition reaction, which produces covalent bonding between sulfur atoms and the nanotube surfaces. Raman, TEM, and photoemission results are consistent with the formation of covalent S-C bonds on the sidewalls. DFT calculations also support a formation of sulfur-carbon bonding and predict electronic and vibrational states that are in good agreement with the experimental results. Based on a comparison between theory and experiments, we propose a stable episulfide (GS) grafting, which consists of of a sulfur atom bridging two carbon atoms repeated over the nanotube surface.

(Invited) Near-Infrared Triggered Theranostics

In the last decade, the field of luminescent lanthanide doped nanoparticles has had a meteoric rise, progressing from the basic understanding of the photophysical properties governing their nanoscale luminescence, in particular upconversion, to their use in a plethora of applications, with considerable focus in biology and medicine. This interest stems primarily from the ability to stimulate these luminescent nanoparticles with near-infrared (NIR) light as well as their diverse emission wavelengths spanning the UV to the NIR. Therefore, with a single NIR excitation wavelength, it is possible to observe higher energy multiphoton luminescence, known as upconversion, or single photon NIR emission (known as down-shifted luminescence). The former upconversion process proceeds through the sequential absorption of multiple NIR photons through the long-lived 4f electronic energy states of the tri-positive lanthanide ions. As a result, upconversion is several of orders more efficient than conventional multiphoton absorption processes. This is especially interesting for applications in theranostics (therapy + diagnostics on the same platform) where the upconverted light can be used to trigger another light activated modality (therapy) while the NIR luminescence can be used for bioimaging and nanothermometry (diagnostics). Here, we present our work on the synthesis and development of various NIR excited (and emitting) core/shell lanthanide-doped nanostructures/nanoplatforms and demonstrate how their various emissions could be harnessed for applications in biology and nanomedicine.

Exploring New Carbon Allotropes and Nanographenes on Surfaces

The quest for planar sp2-hybridized carbon allotropes other than graphene has stimulated substantial research efforts because of their predicted unique mechanical, electronic, and transport properties. However, the syntheses of these nonbenzenoid networks remain challenging due to the lack of reliable protocols for generating nonhexagonal rings. We have developed various on-surface synthesis strategies by which straight polymer chains are linked to form the nonbenzenoid carbon networks. In this way, we synthesized biphenylene network, a new carbon allotrope with 4-6-8-membered rings, which is metallic already at very small dimensions. Similarly, we generated phagraphene nanoribbons, which are based on 5-6-7-membered rings.Acenes are another interesting class of carbon materials that have fascinated chemists and physicists due to their potential for use in organic electronic applications. We show the synthesis of tridecacene (13ac) and pentadecacene (15ac), the longest acenes known to date, via multistep single-molecule manipulation of suitable precursor molecules on Au(111). We find antiferromagnetic open-shell ground state electron configurations for both acenes. 15ac shows a low-bias spin-excitation feature, indicating a singlet-triplet gap of around 124 meV. Investigation of 15ac complexes with up to 6 gold atoms suggest considerable multiradical contributions to the electronic ground state of 15ac.Altering the electronic and magnetic properties of carbon-based nanomaterials can also be achieved by doping with heteroatoms. We present an access to a variety of nitrogen-containing 0D and 1D carbon nanostructures including planar and curved cycloarenes with different cavities as well as N-doped graphene nanoribbons.

Novel Functional Organic Chromophores

Porphyrins and other tetrapyrroles are highly suitable for sensing operations based on their synthetic flexibility and chromophore structures where an analyte might interact to stimulate some variation in directly observable optical colour or fluorescence emission modulation. Their chromophore structures also allow access to electronic triplet states, which can be harnessed for the generation of singlet oxygen – a highly reactive species useful for photodynamic action against tumours or microorganisms. Here we discuss the sensing activity of several β-substituted porphyrins1 including not only by the introduction of suitable interacting units but also by the adaptation of non-planar porphyrins for the synthesis of porous structures. The latter are applied for film formation and sensing involving nanomechanical sensors. Selectivity and mechanisms of sensing activity are discussed. We will also introduce new efficient singlet oxygen generating materials based on agglomeration of an oxidized porphyrin chromophore as metal-organic frameworks,2 electron deficient porous polymers, or using resorcinarenes.3 The use of these materials for selective oxidation of organic substrates is demonstrated. Overall, the results demonstrate the efficacy of the chromophore approach to functional materials. The self-assembly properties of porphyrins and nitrogen rich acene compounds, the pyrazinacenes, will also be considered based on contrasting cases of on-surface mobility and immobility, and the introduction of particular functionality influencing the resulting supramolecular structures.

(Invited) Enabling Bio-Realistic Artificial Intelligence Hardware with Neuromorphic Nanoelectronics

The exponentially improving performance of digital computers has recently slowed due to the speed and power consumption issues resulting from the von Neumann bottleneck. In contrast, neuromorphic computing aims to circumvent these limitations by spatially co-locating logic and memory in a manner analogous to biological neuronal networks [1]. Beyond reducing power consumption, neuromorphic devices provide efficient architectures for image recognition, machine learning, and artificial intelligence [2]. This talk will explore how low-dimensional nanoelectronic materials enable gate-tunable neuromorphic devices [3]. For example, by utilizing self-aligned, atomically thin heterojunctions, dual-gated Gaussian transistors have been realized, which show tunable anti-ambipolarity for artificial neurons, competitive learning, spiking circuits, and mixed-kernel support vector machines [4,5]. In addition, field-driven defect motion in polycrystalline monolayer MoS2 enables gate-tunable memristive phenomena that serve as the basis of hybrid memristor/transistor devices (i.e., ‘memtransistors’) that concurrently provide logic and data storage functions [6]. The planar geometry of memtransistors further allows multiple contacts and dual gating that mimic the behavior of biological systems such as heterosynaptic responses [7]. Moreover, control over polycrystalline grain structure enhances the tunability of potentiation and depression, which enables unsupervised continuous learning in spiking neural networks [8]. Finally, the moiré potential in asymmetric twisted bilayer graphene/hexagonal boron nitride heterostructures gives rise to robust electronic ratchet states. The resulting hysteretic, non-volatile injection of charge carriers enables room-temperature operation of moiré synaptic transistors with diverse bio-realistic neuromorphic functionalities and efficient compute-in-memory designs for low-power artificial intelligence and machine learning hardware [9].[1] V. K. Sangwan, et al., Matter, 5, 4133 (2022).[2] V. K. Sangwan, et al., Nature Nanotechnology, 15, 517 (2020).[3] M. E. Beck, et al., ACS Nano, 14, 6498 (2020).[4] M. E. Beck, et al., Nature Communications, 11, 1565 (2020).[5] X. Yan, et al., Nature Electronics, DOI: 10.1038/s41928-023-01042-7 (2023).[6] X. Yan, et al., Advanced Materials, 34, 2108025 (2022).[7] H.-S. Lee, et al., Advanced Functional Materials, 30, 2003683 (2020).[8] J. Yuan, et al., Nano Letters, 21, 6432 (2021).[9] X. Yan, et al., Nature, DOI: 10.1038/s41586-023-06791-1 (2023).

(Invited) Epitaxial III-V Nanomaterials on the Si Platform for Quantum and Data Communications

As Si-based integrated photonic components begin to replace older technologies for optical data communications, the need for better integration of semiconductor lasers on the Si platform is greater than ever. In addition, emerging interest in integrated-photonic-based quantum computing and quantum sensing presents a further need for quantum light emitters—entangled and single-photon—on Si. III-V quantum dots represent a promising solution, both for the active region of telecommunications-wavelength lasers and for quantum emitters. However, epitaxial quantum dots grown on conventional (100) substrates typically lack the high symmetry required for entangled-photon emission.This presentation will discuss our recent work to develop a novel approach for III-V direct growth on Si via an ultrathin (<10 nm) single crystal strain relieving buffer layer, realized by the selective oxidation and condensation of an amorphous SiGe surface layer. The fabrication and properties of this novel Ge-rich buffer layer, as well as its use for subsequent III-V organometallic vapor-phase epitaxy will be presented.The second part of the talk will present our recent work on the epitaxial growth and characterization of (In,Ga)As quantum dots for the above-mentioned applications. Specifically, I will show that surface-energy-modifying surfactants (Sb, Bi) present the possibility to externally direct quantum dot formation “on-demand” in strained InAs layers on GaAs(111) substrates, where quantum dot formation by the Stranski–Krastanov process does not naturally occur. These nanostructures are prospective for high-symmetry entangled-photon emitters. The three-dimensional (3D) composition profile of InAs quantum dot layers is characterized by atom-probe microscopy (APT), elucidating the real-world quantum dot matrix. This 3D composition data is input into a finite element solver to determine the quantum dot energies and wavefunctions for electrons and holes. The modeling reveals that in high-density quantum dot layers, the electron and hole states are hybridized between multiple quantum dots in the matrix. This has important consequences for design of quantum dot light emitters. The predicted transition energies are in agreement with low-temperature photoluminescence. This work constitutes a promising approach for integrating telecommunications-wavelength quantum dot lasers and entangled photon emitters on the Si integrated photonics platform.

Telecom Photon Emitters Based on Isolated Group-IV Quantum Dots Deterministically Coupled to High-Q Photonic Crystal Cavities

The realization of scalable telecom light emitters that can be monolithically implemented into large-scale Si integration technology has been a driving factor in the field of Si photonics for the last decades. Applications are envisioned in the short and medium-range data transfer and for realizing scalable, Si-based quantum information technology. For the latter, CMOS-compatible sources that can be controlled on the single photon level are needed. In solid-state materials, group-III-V quantum dots (QDs) are one of the leading platforms for realizing single photon emitters of excellent optical quality [1,2]. However, their emission outside the telecom band and the difficulty of combining them with the mature Si photonics components such as waveguides remain an ongoing problem.In the group-IV (SiGe) system, the bandgap of the bulk materials is indirect, and electron and hole states in QDs are spatially separated due to the type-II band alignment. These material properties lead to relatively long radiative lifetimes and small emission efficiencies. However, for Si/SiGe QDs grown on silicon on insulator substrates (SOI), these efficiencies can be strongly and deterministically Purcell-enhanced by aligning photonic crystal cavities with single QDs [3]. One necessary prerequisite is, therefore, to achieve perfect nucleation site control of the QDs on the substrates [4,5]. This nucleation control can be achieved by deterministic substrate patterning combined with Ge growth in the supersaturation regime of the two-dimensional wetting layer [6], utilizing Ge's extensive surface diffusion lengths at growth temperatures above 600°C [7]. In such a way, it is possible to grow isolated QDs with virtually arbitrary inter-QD distance [4,5].Here, one isolated QD was grown on a substrate area of the size of 100´100 µm2 [8]. We demonstrate the accurate QD positioning in PhC cavities [3,8], particularly in bichromatic cavities. Bichromatic cavities, a relatively novel design of photonic crystal cavity, offer ultra-high quality factor, and therefore Purcell enhancement, that is achievable with simple design rules [9]. Unlike in standard line defect cavities, in the present bichromatic layout, the line defect consists of a periodic sequence of holes, leaving only narrow Si regions.For this reason, an extremely high accuracy for QD positioning is required, which can be provided by interlacing site control of QD growth and PhC cavity formation. In micro photoluminescence spectra, the modes of single cavities are clearly observed. From the dependence of the mode intensities on the temperature and the excitation intensity, modes fed by the single QD in the cavity can be identified. We observe ultra-high quality factors of up to 100,000 for the modes coupled to QDs [8]. For resonators loaded with a QD, such high Q-factor values are record-high for the silicon-on-insulator integrated optics platform. Results on the excited state lifetime will be discussed.[1] D. Huber et al., Phys. Rev. Lett. 121, 33902 (2018)[2] N. Somaschi et al., Nature Photonics 10, 340 (2016)[3] M. Schatzl et al., ACS Photonics 4, 665 (2017)[4] M. Grydlik et al., Nanotechnology 24, 105601 (2013)[5] M. Brehm, et al., Nanotechnology 28, 392001 (2017)[6] M. Brehm, et al., Physical Review B 80 (20), 205321 (2009)[7] M. Grydlik et al., Physical Review B 88 (11), 115311 (2013)[8] T. Poempool et al., Optics Express 31 (10), 15564-15578 (2023)[9] A. Simbula et al., APL Photonics 2, 056102 (2017).