In this study, we experimentally demonstrate that the magnetic properties of nitrogen-doped graphene (NG) are influenced by the configuration of nitrogen dopants, namely graphitic, pyridinic, and pyrrolic, along with the overall nitrogen concentration. The NG materials were prepared via a two-step thermal treatment process. The first step involved heating in ammonia at 400 °C, followed by a second post-annealing step at 600 °C. Scanning Electron Microscopy–Energy Dispersive X-ray Spectroscopy (SEM–EDS) analysis performed at 25 μm resolution confirmed uniform elemental distribution across the samples. X-ray photoelectron spectroscopy (XPS) revealed that while the total nitrogen content decreased from 11.9 at.% in NG to 5.5 at.% in the post-annealed sample, the ratio of graphitic to pyrrolic nitrogen increased from 0.4% to 3.8% and the ratio of graphitic to pyridinic nitrogen increased from 0.8% to 2.5%. Raman spectroscopy confirmed the presence of prominent D and G bands at ~1352 cm−1 and ~1589 cm−1, respectively, along with a 2D band at ~2692 cm−1, indicating the presence of few-layered graphene and defect-related features. The IDIG ratio increased from 1.12 to 1.27 in the post-annealed sample, indicating increased disorder after annealing. Magnetic characterization showed a marked enhancement in the magnetic properties with increased graphitic nitrogen content. The saturation magnetization (Ms) reached 0.13 emu g−1, ~42% higher than that of the material heated in ammonia, with the coercivity increasing from 40 Oe to 750 Oe. These results emphasize the pivotal role of nitrogen configuration in the graphene host, specifically the promotion of graphitic nitrogen species, in tailoring the ferromagnetic response of NG.

We report a chemical vapor deposition method where transition metal dichalcogenide growth is modified by changing the thickness and stacking sequence of patterned Mo and W composite films. The top metal thickness was kept constant at - 200 nm while the bottom metal thickness was varied. For samples with W covered by Mo with W:Mo thickness ratios of approximately 1:20, 1:4 and 1:1, Mo1-xWxS2 alloys were formed with concentrations of approximately 0-0.25, 0.25-0.50 and 0.75-1, respectively. With the stacking order reversed, there was no identifiable Mo present in the growth from the 1:20 and 1:4 Mo:W samples; however, for 1:1 Mo:W samples, about one third of the material had a concentration of - 0.25 while the remaining two thirds had a concentration of 0.75-1.0.

High-quality two-dimensional transition metal dichalcogenides (2D TMDs), such as molybdenum disulfide (MoS2), have significant potential for advanced electrical and optoelectronic applications. This study introduces a novel approach to control the localized growth of MoS2 through the selective oxidation of bulk molybdenum patterns using Joule heating, followed by sulfurization. By passing an electric current through molybdenum patterns under ambient conditions, localized heating induced the formation of a molybdenum oxide layer, primarily MoO2 and MoO3, depending on the applied power and heating duration. These oxides act as nucleation sites for the subsequent growth of MoS2. The properties of the grown MoS2 films were investigated using Raman spectroscopy and photoluminescence measurements, showing promising film quality. This study demonstrates that Joule heating can be an effective method for precise control over TMD growth, offering a scalable approach for producing high-quality 2D materials that have the potential to be integrated into next-generation electrical and optoelectronic technologies.

Chemical vapor deposition (CVD) is the most common fabrication method for transition metal dichalcogenides (TMDs) where direct chemical vapor phase reaction between an oxide transition metal and chalcogen powder results in formation of high-quality crystals of TMDs. However, in this method the nucleation is often random with incomplete nucleation and non-uniform thickness. In this work we studied the formation of a localized transition metal oxide which resulted in controllable growth of mono- to few-layer MoS _2 around the formed oxide region. Bulk molybdenum patterns were irradiated with a 532 nm continuous wave laser creating a localized hot-spot which, under ambient conditions, resulted in the formation of molybdenum oxide. The characteristics of the subsequent MoS _2 growth depended on the type and thickness of the MoO _x which was determined by the power and duration of laser exposure. The resulting MoO _x and MoS _2 growth around the localized oxide regions were investigated by Raman and photoluminescence spectroscopy. Our studies have shown that exposing bulk molybdenum patterns to 10 mW of laser power for about 2s results in the minimal formation of MoO _2 which coincides with high quality mono- to few-layer MoS _2 growth.

Transition metal dichalcogenides such as MoS2, which can be produced in monolayer form, have attracted attention because of their interesting and potentially useful electrical and optical properties. These properties often depend sensitively on material properties such as defect density and crystallinity. Herein, the effects of postgrowth annealing on monolayer MoS2 grown using a novel chemical vapor deposition process are investigated. In this process bulk molybdenum patterns serve as the nucleation site and source material for high‐quality MoS2 material growth. After postgrowth thermal annealing, the photoluminescence is found to blueshift and become more uniform up to an annealing temperature of 300 °C. At higher temperatures, isolated monolayers begin to crack along the grain boundaries, which leads to variations in luminescence, whereas after annealing temperature of 200 °C, material anchored to the molybdenum patterns is found to easily ablate.

A chemical vapor deposition (CVD) growth model is presented for a technique resulting in naturally formed 2D transition metal dichalcogenide (TMD)-based metal-oxide-semiconductor structures. The process is based on a standard CVD reaction involving a chalcogen and transition metal oxide-based precursor. Here however, a thin metal oxide layer formed on lithographically defined contacts composed of pure bulk transition metal serves as the precursor. The chalcogen reacts with the metal oxide, leading to the growth of highly crystalline films, which display strong luminescence, monolayer Raman signatures, and relatively large crystal domains. Raman spectroscopy and cross-sectional SEM studies provide insight into the characteristics of the metal oxide and its effect on the TMD growth. The TMD material migrates outward along the substrate while remaining connected to the lithographically defined contacts, offering a scalable path for producing as-grown, naturally contacted, two-dimensional material-based devices.

Coupled quantum dots (CQDs) that consist of two InAs QDs stacked along the growth direction and separated by a relatively thin tunnel barrier have been the focus of extensive research efforts. The expansion of available states enabled by the formation of delocalized molecular wavefunctions in these systems has led to significant enhancement of the already substantial capabilities of single QD systems and have proven to be a fertile platform for studying light-matter interactions, from semi-classical to purely quantum phenomena. Observations unique to CQDs, including tunable g-factors and radiative lifetimes, in situ control of exchange interactions, coherent phonon effects, manipulation of multiple spins, and nondestructive spin readout, along with possibilities such as quantum-to-quantum transduction with error correction and multipartite entanglement, open new and exciting opportunities for CQD-based photonic quantum technologies. This review is focused on recent CQD work, highlighting aspects where CQDs provide a unique advantage and with an emphasis on results relevant to photonic quantum technologies.

The difficulty of processing two-dimensional (2D) transition metal dichalcogenide (TMD) materials into working devices with any scalability is one of the largest impediments to capitalizing on their industrial promise. Here, we describe a versatile, simple, and scalable technique to directly grow self-contacted thin-film materials over a range of TMDs (MoS2, MoSe2, WS2, and WSe2), where predeposited bulk metallic contacts serve as the nucleation site for the TMD material to grow, forming naturally contacted device structures in a single step. The conditions for growth as well as optical and physical properties are reported. Because the material grows controllably around the lithographically defined patterns, wafer scale circuits and complex device geometries can be envisioned, including lateral heterostructures of different TMD materials.

We will present a chemical vapor deposition process to selectively grow 2D materials in a deterministic manner around lithographically defined bulk metallic patterns which concurrently provide asgrown electrical contact to the material [1]. With this process, monolayer films, with lateral extent of up to hundreds of microns are controllably grown on and around patterned regions of transition metals. The materials display strong luminescence, monolayer Raman signatures, and relatively large crystal domains. In addition to producing high optical quality monolayer material, the metallic patterns remain conductive providing as-grown metallic contacts to the material. Preliminary results (Figure 1) have demonstrated the feasibility of this process through the direct growth of MoS2 based metal-semiconductor-metal photodiodes and Schottky barrier FET devices. Since the material grows controllably around the lithographically defined patterns, complex device structures and wafer scale circuits can be envisioned. Preliminary results also indicate the technique has the added potential of producing self-contacted heterostructured devices as well as the possibility of controllable doping of the 2D material using alloyed metallic contacts. This is the first report of using bulk metallic patterns resulting in as-grown, self-forming, electrical contact to the monolayer material, providing a simple, scalable, and reproducible method for creating 2D materials-based devices with broad implications for basic research and industrial applications.

Scalable fabrication of two-dimensional materials-based devices with consistent characteristics remains a significant impediment in the field. Here, we report on as-grown monolayer MoS2 metal-semiconductor-metal photodetectors produced using a CVD process which results in self-contacted two-dimensional material-based devices. The photodetectors show high responsivity (∼1 A/W) even at a low drain-source voltage (VDS) of 1.5 V and a maximum responsivity of up to 15 A/W when VDS = 4 V with an applied gate voltage of 8 V. The response time of the devices is found to be on the order of 1 μs, an order of magnitude faster than previous reports. These devices demonstrate the potential of this simple, scalable, and reproducible method for creating as-grown two-dimensional materials-based devices with broad implications for basic research and industrial applications.

While new species and properties of two-dimensional (2D) materials are being reported with extraordinary regularity, a significant bottleneck in the field is the ability to controllably process material into working devices. We report a chemical vapor deposition process to selectively grow 2D material in a deterministic manner around lithographically defined bulk metallic patterns which concurrently provide as-grown contacts to the material. Monolayer films, with lateral extent of up to hundreds of microns are controllably grown on and around patterned regions of transition metals. By using different combinations of metallic pattern and oxide based precursor, heterostructured MoS2/WS2 growth has been observed as well. The materials display strong luminescence, monolayer Raman signatures, and relatively large crystal domains. In addition to producing high optical quality monolayer material deterministically and selectively over large regions, the metallic patterns remain conductive and therefore have the advantage of providing as-grown metallic contacts to the material, offering a path for simple device fabrication and large scale production