Scientists continue relentlessly to ramp up the transformative ability of electronic devices. And with their ubiquitous applicability, electronic devices have remained the main driving force propelling technological advancements in various facets of life.
This latest innovation in electronic devices, which is poised to make for faster and more efficient electronic devices, comes in the wake of the discovery of new techniques to manipulate electrons.
The innovation is the fruits of a research carried out by a team of scientists from the Femtosecond Spectroscopy Unit of the Okinawa Institute of Science and Technology Graduate University (OIST). The study, which has been published in the journal Science Advances, centers around a new mechanism which utilizes light to facilitate the control of electrons on the nanometer (10-9 of a meter) spatial scale and femtosecond (10-15 of a second) temporal scales.
The Brass Tacks of the Latest Innovation
Basically, the operations of electronic devices pivot around the fact that a voltage circulating a semiconducting material generates an electric field which directs the movement of electrons around the material. In the OIST studies, Dr. E Laine Wong, together with her colleagues harnessed a physical phenomenon known as photovoltage effect to generate an electric field which allows them to direct the flow of electrons in opposite directions. The photovoltage effect refers to the possibility of changing the surface potential of a material by altering light intensity.
Dr. Wong and her team seized upon this phenomenon by developing a setup in which a laser beam with a non-uniform intensity profile facilitates the manipulation of local surface potentials, allowing for the creation of electric fields that vary spatially and temporally within the photoexcitation spot. In effect, the set up allowed the researchers to control the movement of electrons on a local surface.
The team of researchers recorded the spatial and temporal dimensions of the electron flow using a combination of femtosecond spectroscopy and electron microscopy techniques.
The femtosecond spectroscopy technique, which furnishes measurements on a femtosecond timescale, allows scientists to study the nitty-gritty of electron excitation on highly ephemeral time scales. The technique entails the use of an ultrafast laser beam dubbed the ‘pump’ to excite electrons on a local site, and then afterward, the use of a second ultrafast laser beam dubbed ‘probe’ to project light beams into the photoexcitation spot to allow the team to monitor the behaviors of the excited electrons.
By incorporating an electron microscope — which offers spatial resolutions — with the femtosecond spectroscopy, the scientists were able to directly image the flow of excited electron within the hairsbreadth cross-section of the photoexcitation spot, which is the point of the incidence of the laser beam. By developing a system that combines the two techniques together, the team of researchers was able to obtain both spatial and temporal resolutions of the controlled flow of elections.
The Techniques for Controlling the Movement of Photoexcited Electrons
The team of researchers deployed techniques for directing oppositely charged as well as like-charged electrons in different directions to control the movement of photoexcited electrons. By deploying such a technique on an ultrafast timescale, the team of researchers was tapping into a ground-breaking new paradigm in optoelectronic control.
But one of the biggest challenges which the team of researchers faced was the need for the proactive modulation of the subpopulations of the photoexcited electrons, especially given the ultrafast timescales they had to work with.
The team ventured to resolve this challenge by developing a technique for monitoring the distribution of photoexcited electrons. First, they harnessed the variations in the spatial intensity of an ultrafast light pulse to generate electric fields in the locality of the optical spot of a charged semiconductor. This allowed them to redirect electrons via two separate distributions.
And through the use of photoemission microscopy, the team then recorded a movie of the distribution protocols spanning a few hundred picoseconds. The team controlled the distribution protocols by regulating the spatial profile of the ultrafast light pulse.
The quantitative model which the team uses to describe the principles guiding the distribution protocol serves up a bona fide blueprint for manipulating the dynamics of photocarrier distributions in spatiotemporal resolutions. Generally speaking, the applications of this model in developing electronic devices hold tremendous potentials for a plethora of technologies.
This latest development of new ways to control the flow of electrons is breaking new grounds given that it uses the spatial profile variations of laser pulses to allow for the control of electron flow beyond light’s resolution limit within the photoexcitation spot. This opens up the possibilities for creating nanoscale electronic devices.