Photon-Induced Near-Electron Microscopy Essay

The advantages of the NEGF formalism and the underlying powerful machinery of the MBPT inspired us to develop the formal NEGF theory of photoemission further with our work [E3]. We elucidated the connection of the formal concepts of the FPA to the standard MBPT, allowing for a practical implementation of the theory. The main advances were achieved by the extension of the theoretical description of DPE, which we advocate as a very useful sensor for the many facets of correlations in many-body systems. The effective electron-electron interaction in more complex systems comprises, besides the Coulomb repulsion, fluctuation-mediated effects due to the dynamical environment. As an important example, we focused on dynamical screening mediated by charge-density fluctuations. We have chosen the buckminster fullerene as a concrete system for its pronounced plasmon resonances and generally rich physics. In our work [E4] we rigorously categorised the collective modes, based on full-fledged ab initio calculations, with the help of the NMF. The obtained model for DD response function – whose accuracy is corroborated by comparing to EELS data – was then employed to characterise the dynamically screened interaction in the C60 molecule. With these tools at hand, we were able to elucidate the role of electronic correlations mediated by the density oscillations in DPE in our joint theoretical and experimental work [E5]. The distinct feature of the experiment – the significant narrowing of the coincidence spectrum – is in agreement with our ab initio description and so endorses the plasmon-assisted DPE due to as a novel aspect of releasing two correlated electrons from complex

Previous/current Graduate Research. Entering graduate school I expanded my interest with the electricomagnetic spectrum in the nanoscale by researching topics such as: computational simulations of nanoantenna (NA), desalination via dielectric breakdown, and hydrogen evolution reactions (HER). Metallic gold (Au) nanoantenna onto two-dimensional (2-D) transition metal dichalcogenides (TMDs) exhibit extraordinary optical properties that allow nanoscale energy modulation. A localized surface plasmon resonance (LSPR) emerges when incident electromagnetic energy excites the conduction electrons, causing them to oscillate coherently on the surface of the NA at a resonant wavelength. The LSPR energy is dissipated into the environment via re-radiation, electron-phonon (lattice vibration) and subsequent phonon-phonon coupling, causing a rise in local thermal energy, and hot electron transfer. Therefore projects such as dimers, nanorods and prisms have become of my interest for they have an electric near field that enhances the surface plasmon resonance to 2-dimensional materials for (TMDs). Conversations with my advisor are ideal when it comes to

The purpose of experiment 9 is to use stimulation to observed the shape of molecules. This stimulation follows the valence shell electron pair repulsion theory to show the basic shapes of molecules and its effects on polarity. The shapes of molecules are represented by molecular and electron geometry. The electronic shape is determined by the number of electron domains, which include lone pairs and bond pairs. An example from the stimulation is H2O, which has 2 bonding pair and 2 lone pair. Therefore, it has four electron domain and is considered to have a tetrahedral electronic shape. However, the molecular geometry is not tetrahedral because molecular geometry only counts the bond pair as electron domain. Hence, the molecular

An anode finger was a pencil-sized tube with a small aperture at the top. Magnetic coils sprayed the electrons emitted from the electrical image left to right and line-by-line onto the aperture, where they became electric current. Both Zworykin’s and Farnsworth’s devices then transmitted the current to a cathode-ray tube, which recreated the image by scanning it onto a fluorescent surface.

Through the use of Smalley’s advance laser, laurites were able to create clusters of carbon 60 and 70 atoms (The Discovery). These “buckyballs” formed when graphene was evaporated into an inert atmosphere at very high temperatures (The Discovery). Their unique nanospheric structure gave birth to new questions, ultimately expanding the field of practical uses in the real world today.

The development of ultrafast electron microscopy was a revolution step in the field. UEM allows for connect the ultrafast electron diffraction dynamics measurement with the structure morphology of the sample under study. Barwick et al. [82] utilized the UEM to study the structural dynamics and morphological changes in single crystal gold and graphite films. In this study, the structure change of specific area of the sample was altered by ultrafast laser pulse by local heating while image frames and diffraction patterns were recorded at different instants of time. In the beginning, a single-crystal thin film (11nm) of gold was illuminated with the laser pulse

This showed that electrons have wave-particle duality like the Light and it exists in a ‘superposition’ which is a state of potential innumerable possibilities of existence. However, what further astounded the physicists was when a detector was placed to measure the passage of electrons to learn how it passes through both slits; the electrons immediately collapsed their wave function

| A beam of electrons (q = 1.6  10–19 C) is moving through a region of space in which there is an electric field of intensity 3.4  104 V/m and a magnetic field of 2.0  10–3 T. The electric and magnetic fields are so oriented that the beam of electrons is not deflected. The velocity of the electrons is approximately

A TEM instrument is designed with an electron gun positioned at the top of the device as the source of electron generation. These electrons are then accelerated to high voltage values to minimise divergence and then are focused into a continuous electron beam with magnetic lenses and apertures. The chamber is in vacuum to protect the beam from scattering along with maintaining a clean working environment. This tool requires very small and thin specimens for analysis such that electrons are able to penetrate through the material lattice without scattering at an angle. These transmitted electrons that go through the sample can form an image at the

The STM works by scanning a very sharp metal wire tip over a surface. By brining the tip very close to the surface, and by applying an electrical voltage to the top or sample, we can image the surface at an extremely small scale-down to resolving individual atoms. The STM is based on several principles. One is the quantum mechanical effect of tunneling.

Breaking the limits of picosecond temporal resolution (600 fs) in electron diffraction measurements were first reported in Siwick et al. [15]. This gave the access to the atomic motion in the photo-induced solid-liquid phase transition (melting) process of Aluminum. In this study, the long-order change traced as a function of time. The 20-nm-thick Al sample was excited by a laser pulse fluence of 70 mJ/cm2. The long-range order (present in the crystalline phase) disappear and a short-range atomic correlation (present in the liquid phase) were emerged which is a clear indication of a complete phase translon process within 3.5 ps (Fig. 7a).

Recent progress in ultrafast lasers gained a lot of interest to investigate ever faster physical processes in atoms, molecules, and solid state surfaces. This advancement gave birth to a broad field of science crossing physics, chemistry, and biology; known as “Ultrafast Science” for which Zewail got the Nobel prize in 1999. But, following electron dynamics in real time, watching the formation or breaking of chemical bonds, or the transfer of electrons from one constituent to another has been a dream and challenge for a long time in this field. The never-ending quest to study the time-resolved dynamics (also known as “Ultrafast molecular movies”) pushing the probes to attosecond (10-18 seconds) and even zeptosecond (10-21 seconds) domain. Only with the advent of attosecond pulse generation, time-resolved dynamics near the ground state (the period of a Bohr orbit ≈ 150 as) came into reach. These ultrafast electric field probes can be used to drive electrons with petahertz (1015 Hz) frequencies also in nanometer scale systems (a new research domain known as “lightwave electronics” is emerged from this idea).

Extraordinary optical transmission (EOT) through nanohole arrays has been concentrated broadly in several aspects, including the hypothesis and confirmation of its origin parameters influencing its intensity, the optical properties, for example like its transmission spectra and divergence. Several parameters including the refractive index of the medium on the metal film surface, the wavelength and condition of polarization of the incident light, the holes shape and periodicity of the structures change the spectral behavior in term of intensity and position of the transmitted peaks. The structures that support EOT have discovered their applications in numerous fields including visible spectroscopy, Raman spectroscopy, sub-wavelength optics, nonlinear optics, and photolithography. As the EOT is influenced by parameters like the shape and periodicity of the holes, devices made in light of this marvel will be more sensitive and supports larger selectivity. Regardless of these advantages a large portion of existing use of EOT has been acknowledged on the structures with limited region of coverage. Because of the constrained techniques and choices for fabrication of such structures, the EOT-based devices were fabricated with finite array sizes. This paper deals with two methods that deals with two methods to produce arrays of nanoholes with sizes of

In a PIN Photodiode, electron hole pairs are generated due to the absorption of photons. The Avalanche Photodiode is very similar to the PIN diode, but the reverse bias voltage applied to this diode is very high. The

This work aims to demonstrate petahertz optical-field-induced current signal control in electronic nanocircuit utilizing synthesized femtosecond light fields. That promises an increase in the speed of data processing and information encoding on rates that exceed 1 Pbit/sec, million times faster than the current technology. It will likely extend the frontiers of modern electronics and information processing technologies into the PHz realm. This work will have a broad impact on the advancements of nanophotonics technologies, most notably in fiber-based telecommunications networks and the photonic computing field and opening a new realm of information technology.