Photonics - Page 7

Researchers from the University of Luxembourg developed a new materiel which resembles graphene but is made from "traditional semiconductor materials". This so-called "artificial graphene" could be useful in many applications, including electronics, optics, solar cells, lasers and LEDs.

The artificial graphene has the same honeycomb structure as graphene, but it uses nanometer-thick semiconductor crystals instead of carbon atoms. The material's properties can be tuned by changing the size, shape and chemical nature of those nano crystals.

Researchers from the University of Utah developed a new way to develop large arrays of graphene nanoribbons (GNRs), aiming for applications in photodetectors. Their method can directly write a large array of 15nm GNRs on a multilayer epitaxial graphene sheet using Focused Ion Beam (FIB).

The researchers accelerated ga+ ions to 30 keV in vacuum using a FEI Helios NanoLab 650 dual-beam FIB machine. This removed carbon atoms from the graphene sheet with a 1.3 sputtering yield (carbon/Ga+ ratio). This technology can be easily transferred to pattern other graphene nanostructures such as spheres, rings and blocks.

Researchers from Korea developed a new skin cancer photothermal therapy using graphene oxide. The idea is to attach the GO particles to tumor cells, and then shine near-infrared laser light on them. The GO generate heat (and destroy the tumor cells) when exposed to the light, while healthy cells are not effected. Graphene is more efficient than gold for converting the light into heat, and it's also cheaper.

The researcher coupled the graphene with hyaluronic acid, a sugar polymer that is found naturally in skin and is an ingredient in skin care products. The polymer can penetrate the skin’s top layer, and tumor cells are known to express a large number of hyaluronic acid receptors on their surfaces. So this coupling allows the researchers to apply the graphene oxide particles to the skin, avoiding the need to inject them.

Researchers from the SLAC lan in Stanford University developed a new method to make 2D material molybdenum diselenide or MoSe₂ that has possible applications in photoelectronic devices, such as light detectors and solar cells, and perhaps also novel electronic devices.

This is the first time single-layer MoSe₂ has been efficiently produced. The method they developed is based on molecular beam epitaxy, and starts with molybdenum and selenium, which are heated in a vacuum chamber until they evaporate. The two elements combined as a thin film. By tweaking the process, they managed to create thin films - one to eight atoms thick. Those sheets were grown on graphene substrates. 

Localized hyperthermia is a solid tumor treatment that uses heat (above 43 degrees Celsius) to boost the cytotoxic effects of chemotherapy or radiotherapy and also increases the permeability of tumor cells to drugs. Graphene Oxide is a possible agent because it absorbs light in the near-infrared range.

Researchers from Portugal and Spain studied in vitro laser dosage and cell irradiation exposure time. It was discovered that cell culture temperature (after irradiating cells that had taken up graphene oxide) increases preferentially with laser power rather than with exposure time. Moreover, when the laser power is increased, cell necrosis leads to an increase of cytokine release to the surrounding medium.

Researchers from the University at Buffalo developed a way to identify the electronic properties of individual graphene sheets in a stack of graphene sheets. The method works even when the sheets are covering each other up.

The idea is to shoot a beam of infrared light on the graphene stack, and measure how the light polarization (direction of oscillation) changes when it bounces back from the graphene sheets. The researchers say the new technique is ultra sensitive and it allowed them to examine dozens of sheets in a single stack.

Researchers from Northwestern University and Argonne National Laboratory demonstrating the first growth of graphene on a single-crystal silver substrate. This method could be used to advance graphene-based optical devices (as silver is a widely used material to enhance optical properties) and enable the interfacing of graphene with other two-dimensional materials.

Silver substrates are chemically inert and have a relatively low melting point, which means it is difficult to use CVD technologies. The researchers used a graphite carbon source and deposited atomic carbon (rather than a carbon-based molecular precursor) onto the silver substrate. This allowed them to use low temperature and this process does not need a chemically active surface.

Researchers from the Max Planck Institute in Hamburg demonstrated that graphene can be used to emit terahertz laser pulses with long wavelengths. This has been theorized before, but now the researchers actually proved that it can be done. A terahertz direct emission is useful in science but this is the first time that such a laser was developed.

The researcher explain that while graphene band-gap is usually referred to as a zero bandgap, it does have an infinitesimally small bandgap. But the electrons still behave like those of a classic semiconductor, and the population inversion in graphene only lasts for around 100 femtoseconds, less than a trillionth of a second. This means you cannot use graphene for continuous lasers, but it can be used for ultrashort laser pulses.

A few days ago we reported on Bluestone Global Tech's new graphene based Field Effect Transistors. We have discussed it with BGT and have some more details on this exciting development. So first of all, we reported that the Gray-FETs are currently offered for research only, but BGT says that they are using a fab that can produce these in volume "to meet most demands". So this is suitable for commercial applications.

In fact BGT is already in talks with several academic and industrial customers. Having a standard GFET product can save a lot of time and will enable those customers to develop their own products based on these transistors faster then if they need to first develop the GFET themselves.

Aixtron announced today that China's National Center for Nanoscience and Technology (NCNST) ordered a BM R&D system to grow graphene and CNTs on 2" substrates.

Dr. Qing Dai from NCNST says that their research currently focuses on the characterization of CNTs and on plasmonic properties of graphene. They aim to build nanophotonic devices such as terahertz waveguides. The BM system will also be used to grow 3D nanostructures combining CNT and graphene.