Electronic and photonic molecular materials research group. We're a world top university renowned for the excellence, impact and distinctiveness of our research-led learning and teaching. Coronavirus Covid : latest advice. Electron Beam Lithography. Off Why use EBL? For two main reasons: Scale: it's possible to create nanostructures with dimensions below 10nm. Nanophotonic hosting geometries are the key to optimally collect photons emitted by a single quantum dot.
We have designed and fabricated GaAs nanophotonic structures capable of efficiently launching single photons emitted by embedded InAs quantum dots into silicon photonic integrated circuits. While silicon photonic circuits are promising for large-scale quantum systems, our method supplies a critical functionality that is unachievable with silicon alone.
A challenge is that the self-assembly of quantum dots yields limited control over dot spatial location. Critically, a quantum dot requires precise positioning within its hosting geometry for optimal performance.
To meet this challenge, in collaboration with the Technical University of Berlin, we used cryogenic cathodoluminescence imaging to locate a single quantum dot in a thin GaAs film bonded to a Si 3 N 4 wafer.
We performed unconventional in situ electron-beam lithography to define a nanophotonic hosting geometry precisely aligned to a specific quantum dot. After etching of the III-V layer, we used conventional electron-beam lithography to define a precisely aligned interfacing Si 3 N 4 photonic circuit. Our deterministically generated single quantum-dot device allowed us to demonstrate, without precedent, the generation of triggered and indistinguishable single-photons in a Si 3 N 4 photonic circuit.
Nanophotonic structures enable control of the interaction of light and matter, allowing observation and application of linear, non-linear, quantum optical, and optomechanical phenomena on chip. This control is possible through strong confinement of light in nanostructures. However, dimensional variations of less than 10 nm can lead to large variations in light propagation. Therefore, the fabrication process requires care to achieve reproducible performance — a real necessity not only for applications, but also for cycles of device development.
The core capability of the Division in electron-beam lithography allows routine demonstration of such control in creating nanophotonic devices for various applications. In practical terms, this means that the Division is able to design, through electromagnetic simulations, a nanophotonic structure, fabricate and then measure devices in a virtuous cycle, thus achieving reproducibly high performance.
An example is the development of Si 3 N 4 microring resonators for optical parametric oscillation, for which engineered guided wave dispersion as a function of wavelength and low propagation losses are essential.
Variation of microring width by less than 10 nm allowed control and observation of parameteric oscillation over a wide range of visible wavelengths, from red to green. Detecting, identifying, and sequencing biopolymers is essential to developing new capabilities to diagnose and treat disease. It is particularly important for DNA, considering the genetic aspects of deceases such as cancer. The resulting pattern is then transferred via etching or by depositing other materials.
By iterating a number of steps of this type, complex structures of very short length scales can be built up. Electron beam lithography tools have a certain maximum area that it can write for a fixed stage position know as Write Field. If the pattern to be exposed is more than the size of the write field, the electron beam is blanked, the stage moves by a distance of 1 write field and the writing continues.
To avoid discontinuities or overlaps between write fields known as field stitching errors , an electron beam lithography system has a laser interferometry stage position system that allows stitching of fields with nanometer scale precision. There is almost always a difference between the digital line width in a pattern and the actual developed feature size after processing.
This comes about from electron scattering in the resist. For a well-characterized process, there is generally a fixed difference between the digital size and the actual size, known as bias. This can be implemented by altering all the sizes in the design as appropriate. Pattern fidelity is limited by electron-matter interactions especially in layouts with a high feature density. The electron scattering within the resist and the from the substrate results in undesired exposures of the resist in regions adjacent to the primary incident beam.
This effect is known as the "Proximity Effect" in electron beam lithography. Due to proximity effects, corners in the desired patterns are rounded, gap spacings and linewidths are modified, and certain features may even merge together or disappear completely. E-beam lithography can be also used for mask making and direct writing on non-planar substrates.
Resolution in electron beam lithography is the minimum size of a feature that can be patterned. It depends on the type of the resist used, the thickness of the resist, the type of substrate, and the operating conditions. The maximum writing area for one field with no stage movement is typically mm.
0コメント