Silicon nanocrystals are produced using a two-stage gold ion implantation technique. First stage implantation using low energy ions leads to the formation of an amorphous Si (a-Si) layer. A subsequent high energy Au irradiation in the second stage is found to produce strained Si NCs. An annealing at a temperature as low as 500$^o$C is seen to result in strain free NCs showing quantum confinement effects. Higher temperature annealing of the samples is found to result in growth in size from recrystallization of the a-Si matrix. Raman Scattering, X-ray diffraction (XRD) and Rutherford Backscattering spectrometry (RBS) have been used to study the effect of annealing on the samples and the size of Si NCs formed. The data could be well explained using a phonon confinement model with an extremely narrow size distribution. XRD results go in line with Raman analysis.
We report on the selective creation of spin filltering regions in non-magnetic InGaAs layers by implantation of Ga ions by Focused Ion Beam. We demonstrate by photoluminescence spectroscopy that spin dependent recombination (SDR) ratios as high as 240% can be achieved in the implanted areas. The optimum implantation conditions for the most efficient SDR is determined by the systematic analysis of different ion doses spanning four orders of magnitude. The application of a weak external magnetic field leads to a sizeable enhancement of the SDR ratio from the spin polarization of the nuclei surro…
Cadmium selenide nanocrystal quantum dots (NC-QDs) are site-selectively synthesized by sequential ion beam implantation of selenium and cadmium ions in a SiO2 matrix through sub-micron apertures followed by a rapid thermal annealing step. The size, areal density and optical emission energy of the NC-QDs are controlled by the ion fluence during implantation and the diameter of implantation aperture. For low fluences and small apertures the emission of these optically active emitters is blue-shifted compared to that of the bulk material by $>100\,{\rm meV}$ due to quantum confinement. The emissi…
Metal-Oxide-Semiconductor (MOS) structures containing 74Ge nanocrystals (NC-Ge) imbedded inside the SiO_2 layer were studied for their capacitance characterization. Ge atoms were introduced by implantation of 74Ge+ ions with energy of 150 keV into relatively thick (~640nm) amorphous SiO_2 films. The experimental characterization included room temperature measurements of capacitance-voltage (C-V) dependences at high frequencies (100 kHz and 1 MHz). Four groups of MOS structures have been studied: The 1st - "initial" samples, without Ge atoms (before ion implantation). The 2nd - "implanted" samp…
In the recently discovered class of materials known as topological insulators, the presence of strong spin-orbit coupling causes certain topological invariants in the bulk to differ from their values in vacuum. The sudden change of invariants at the interface results in metallic, time reversal invariant surface states whose properties are useful for applications in spintronics and quantum computation. However, a key challenge is to fabricate these materials on the nanoscale appropriate for devices and probing the surface. To this end we have produced 2 nm thick nanocrystals of the topological …
Layered transition metal dichalcogenides (TMDs) are attracting increasing attention because they exhibit unconventional magnetic properties due to crystal imperfections in their usually non-magnetic 2D structure. This work aims to investigate the magnetic response of self-engineered Se deficient TiSe$_2$ thin films, synthesized using chemical vapour deposition. We demonstrate tunability of the ferromagnetic order with the introduction of Au atoms using low energy Au ion implantation, which works as a controlling knob to vary the stoichiometry of Se in TiSe$_{2-x}$. The corresponding isothermal…
We report a high-throughput and easy-to-implement approach to fabricate microchannels of nanocrystal superlattices with dimensions of ~4 micrometer^2, thus approaching the size of typical single-crystalline domains. By means of microcontact printing, highly ordered superlattices with microscale dimensions are transferred onto photolithographically prepatterned microelectrodes, obtaining well-defined superlattice microchannels. We present step-by-step guidelines for microfabrication, nanocrystal self-assembly and patterning to archive large quantities of up to 330 microchannels per device for s…
Optomechanical resonators were fabricated on a silicon-on-insulator (SOI) substrate that had been implanted with phosphorus donors. The resonators' mechanical and optical properties were then measured (at 6 kelvin and room temperature) before and after the substrate was annealed. All measured resonators survived the annealing and their mechanical linewidths decreased while their optical and mechanical frequencies increased. This is consistent with crystal lattice damage from the ion implantation causing the optical and mechanical properties to degrade and then subsequently being repaired by th…
Nanocrystalline Cu-3 at.% Zr powders with ~20 nm average grain size were created with mechanical alloying and their thermal stability was studied from 550-950 °C. Annealing drove Zr segregation to the grain boundaries, which led to the formation of amorphous intergranular complexions at higher temperatures. Grain growth was retarded significantly, with 1 week of annealing at 950 °C, or 98% of the solidus temperature, only leading to coarsening of the average grain size to 54 nm. The enhanced thermal stability can be connected to both a reduction in grain boundary energy with doping as well as …
Electronic devices based on graphene technology are catching on rapidly and the ability to engineer graphene properties at the nanoscale is becoming, more than ever, indispensable. Here, we present a new procedure of graphene functionalization on SiC(0001) that paves the way towards the fabrication of complex graphene electronic chips. The procedure resides on the well-known ion-implantation technique. The efficiency of the working principle is demonstrated by the intercalation of the epitaxial graphene layer on SiC(0001) with Bi atoms, which was not possible following standard procedures. Our…
Group-IV color centers in diamond have garnered great interest for their potential as optically active solid-state spin qubits. Future utilization of such emitters requires the development of precise site-controlled emitter generation techniques that are compatible with high-quality nanophotonic devices. This task is more challenging for color centers with large group-IV impurity atoms, which are otherwise promising because of their predicted long spin coherence times without a dilution refrigerator. For example, when applied to the negatively charged tin-vacancy (SnV$^-$) center, conventional…
Single dopant atoms or dopant-related defect centers in a solid state matrix provide an attractive platform for quantum simulation of topological states, for quantum computing and communication, due to their potential to realize a scalable architecture compatible with electronic and photonic integrated circuits. The production of such quantum devices calls for deterministic single atom doping techniques because conventional stochastic doping techniques are cannot deliver appropriate architectures. Here, we present the fabrication of arrays of praseodymium color centers in YAG substrates, using…
We present an in-situ counted ion implantation experiment reducing the error on the ion number to 5 % enabling the fabrication of high-yield single photon emitter devices in wide bandgap semiconductors for quantum applications. Typical focused ion beam implantation relies on knowing the beam current and setting a pulse length of the ion pulse to define the number of ions implanted at each location, referred to as timed implantation in this paper. This process is dominated by Poisson statistics resulting in large errors for low number of implanted ions. Instead, we use in-situ detection to meas…
Nitrogen Vacancy (NV) centers in diamond are a platform for several important quantum technologies, including sensing, communication and elementary quantum processors. In this letter we demonstrate the creation of NV centers by implantation using a deterministic single ion source. For this we sympathetically laser-cool single $^{15}\textrm{N}_2^+$ molecular ions in a Paul trap and extract them at an energy of 5.9\,keV. Subsequently the ions are focused with a lateral resolution of 121(35)\,nm and are implanted into a diamond substrate without any spatial filtering by apertures or masks. After …
The fabrication of micro- and nano-scale silicon electronic devices requires precision lithography and controlled processing to ensure that the electronic properties of the device are optimized. Importantly, the Si-SiO2 interface plays a crucial role in defining these properties. While transmission electron microscopy (TEM) can be used to observe the device architecture, substrate / contact crystallinity and interfacial roughness, the preparation and isolation of the device active area is problematic. In this work, we describe the use of focussed ion beam technologies to isolate and trench-cut…
We report on the fabrication and electrical characterization at millikelvin temperatures of a novel silicon single-electron transistor (Si-SET). The island and source-drain leads of the Si-SET are formed by the implantation of phosphorus ions to a density above the metal-insulator-transition, with the tunnel junctions created by undoped regions. Surface gates above each of the tunnel junctions independently control the tunnel coupling between the Si-SET island and leads. The device shows periodic Coulomb blockade with a charging energy e$^2$/2C$_Σ$ $\sim$ 250 $μ$eV, and demonstrates a reproduc…
Annealing has been extensively used to control crystal growth and physical properties of materials with unfortunately unclear mechanism and quantitative correlations. Here we present the "annealing temperature - grain size - band gap" correlation for ZnO nanocrystals with experimental evidence. Findings revealed that the annealing condition determines the critical size by equating the thermal and the cohesive energy of the undercoordinated atoms in the surface skin, which in turn induce local strain and quantum entrapment, perturbing the Hamiltonian and hence the band gap. The formulation prov…
