Roshan Achal's research while affiliated with University of Alberta and other places

... The controlled change of the DB charge state allows to study interesting and complex physical phenomena, making the DBs attractive from the fundamental point of view [7][8][9][10]. From the practical point of view, DBs are promising for many applications in atomic scale silicon-based electronic devices due to the well-developed process of their precise creation on Si(100)-2 × 1-H [11][12][13][14]. ...

... This is because electric charges are shielding the electrostatic field. More precisely, the electrostatic potential Vi,j at position i generated by an SiDB in state nj ∈ {−1, 0, 1} at position j is given by [8], [29] ...

... Recent years have seen an increase in scientific interest in the Silicon Dangling Bond (SiDB) logic platform-an emerging computational beyond-CMOS nanotechnology [1]- [7]. Of particular significance are its sub-nanometer elementary devices that allow for an integration density improvement of several orders of magnitude over current CMOS fabrication nodes [3], [4], [6]- [11]; and its properties to compute Boolean logic without the flow of electrostatic current but, instead, via the Coulombic repulsion of charges [4], [8]. By this, SiDB logic promises ultra-low energy dissipation and establishes itself as a highly-anticipated green competitor in the beyond-CMOS domain [3], [8], [11]- [15]. ...

... Recently, atom manipulation has been extended to platforms including superconductors 9,10 , 2D materials [11][12][13] , semiconductors 14,15 , and topological insulators 16 to create topological and many-body effects not found in naturally occurring materials. In addition, atom manipulation is used to build and operate computational devices scaled to the limit of individual atoms, including quantum and classical logic gates [17][18][19][20] , memory 21,22 , and Boltzmann machines 23 . ...

... Trap states are normally hard to be controlled in conventional semiconductors. However, with the help of STM, the trap states can be introduced more precisely, [134,135] which may find applications in negative differential resistance devices. [136,137] For instance, PbS/(p-type etched) InP with interfacial trapping states are employed in neuromorphic computing through a STM circuit based on single-electron tunneling, acting as both synapses (weighted connections) and spiking elements. ...

... Recent years have seen an increase in scientific interest in the Silicon Dangling Bond (SiDB) logic platform-an emerging computational beyond-CMOS nanotechnology [1]- [7]. Of particular significance are its sub-nanometer elementary devices that allow for an integration density improvement of several orders of magnitude over current CMOS fabrication nodes [3], [4], [6]- [11]; and its properties to compute Boolean logic without the flow of electrostatic current but, instead, via the Coulombic repulsion of charges [4], [8]. By this, SiDB logic promises ultra-low energy dissipation and establishes itself as a highly-anticipated green competitor in the beyond-CMOS domain [3], [8], [11]- [15]. ...

... The bandwidth of the electronics used in STM is typically in the kHz range, Journal of Applied Physics corresponding to a time resolution of milliseconds. 30,31 However, this limitation can be overcome with the use of ultrashort pulsed lasers. 32 Instead of measuring the time evolution of the tunneling current directly, researchers shined ultrashort optical double pulses onto an STM tip and observed tunneling current variations as a function of the time interval between the pulses. ...

... First, we list features that involve only one side of a dimer. These We start with a discussion of silicon DBs, which are wellstudied unterminated silicon atoms [52][53][54]. In STM, the centre of a DB is imaged as a bright protrusion due to its conductive orbital which extends into vacuum. ...

... The locations can be atomically accurate due to the regular surface lattice structure as illustrated in Fig. 1. They were found to behave like quantum dots as their energetic charge transition levels fall within the bulk band gap, allowing them to take on vacant, singly-occupied, or doubly-occupied states corresponding to positive, neutral, and negative charge states [17], [18]. In [5], Huff et al. experimentally demonstrated logic cells, wires, and an OR gate that represented logic states via the location of charges shared between pairs of SiDBs as illustrated in Fig. 1. ...