Via Dr Leonard Coldwell
Here is the Abstract only in English…
Today’s digitalization is largely made possible by connecting digital components and increasing computing power. This has led to applications and research in the last decades that were previously not possible due to the lack of computing power. These include autonomous driving, deep learning and artificial intelligence. The constant technical progress described by Moore’s Law can be traced back to the miniaturiza- tion of components such as transistors. This increases the density of transistors on a processor core and thus its computing power.
However, further compliance with Moore’s Law and thus digital progress cannot be achieved in the future by reducing the size of the components alone. Already today, fundamental physical limits are being reached, such as heat dissipation, which make further miniaturization very difficult. Therefore, alternatives are needed to further increase computing power in the future.
One possibility is massive parallelization. Here hundreds to thousands of cores are connected in parallel to increase the compu- ting power. However, classical on-chip communication methods such as BUS systems are unsuitable for communication between the cores, as they are only scalable to a limited extent. An alternative is wireless communication, as a key technology for complex architectures.
In addition to scalability, this communication technology also has the possibility of reconfiguration and adaptation to current requirements and is therefore perfectly suited for agile network architectures. For this purpose, each core requires an antenna to send signals and receive signals from other cores.
The size of the antenna plays a decisive role here, because miniaturization has made the space on a core very precious. Classical metal antennas emitting at one THz have a length of approximately 7000 transistor channels and are therefore far too large.
With graphene, on the other hand, there is a fundamentally altered relationship bet- ween antenna length and resonance frequency due to the unique material properties. This means that graphene antennas can be up to two orders of magnitude smaller than metallic antennas at the same resonant frequency. The integration of graphene antennas into integrated circuits is therefore ideally suited to realize on-chip commu- nication and thus increase computing power. The research, description, realization and investigation of these antennas is the content of this thesis.
The introduction is followed by the theoretical principles for the description of these antennas. Here, first some important antenna fundamentals are explained and then the fundamental descriptions of plasmons are presented. This is followed by a description of graphene. The chapter concludes with the theoretical treatment of plasmonic graphene antennas.
After considering the current state of research, the measuring and manufacturing methods are explained. First of all, lithography, which is used to manufacture theantenna structure, is discussed. The next point is the description of the TDS measurement setup used to measure the antennas.
Next, theoretical considerations and calculations on the material requirements of graphene follow. The length of the antenna is of crucial importance. Here it is shown that for a functional graphene antenna a good match between antenna geometry and material quality is required.
During the technological realization, after some challenges, a stable manufacturing process could be established. For the characterization of graphene different methods are considered. For this purpose needle measurements on the SEM, TDS transmission measurements and Raman spectroscopy are suitable.
After the production and characterization of graphene, the dipole antennas are mea- sured in the TDS test setup. The first measurements show that, in addition to the antenna effect, charge carriers accelerated by an electrical bias voltage also contribute to the THz emission.
To minimize the influence of this effect, antennas were manufactured and measured in an alternative geometry (H-structure). A clear influence of graphene on the amplitude of the emitted THz radiation was found. The origin of this signal is the concentration of the electric field created by the bias voltage between the antenna arms. These measurements show the first THz emission of a graphene antenna structure.
In order to increase the material quality, samples were produced where either one or both sides of the graphene antenna are covered with hBN. Measurements on these antennas show a significantly increased THz emission due to the concentration of the electric field between the two antenna arms.
Finally, various possibilities to increase the emission of the graphene antenna are presented. There are possibilities to change the sample setup and geometry as well as external influences like doping and temperature
The final conclusion is followed by a critical discussion of the theoretical and practical results of this work and a classification into possible fields of research and application. This work shows the first THz emission of a graphene antenna structure and provi- des detailed theoretical, technological and experimental results, which are needed to realize a functional graphene antenna.