Changyi Yang

Controlled shallow single-ion implantation in silicon using an active substrate for sub-20-keV ions

We demonstrate a method for the controlled implantation of single ions into a silicon substrate with energy of sub-20‐keV. The method is based on the collection of electron-hole pairs generated in the substrate by the impact of a single ion. We have used the method to implant single 14‐keV P31 ions through nanoscale masks into silicon as a route to the fabrication of devices based on single donors in silicon.

Transport Spectroscopy of Single Phosphorus Donors in a Silicon Nanoscale Transistor

We have developed nanoscale double-gated field-effect-transistors for the study of electron states and transport properties of single deliberately implanted phosphorus donors. The devices provide a high-level of control of key parameters required for potential applications in nanoelectronics. For the donors, we resolve transitions corresponding to two charge states successively occupied by spin down and spin up electrons. The charging energies and the Lande g-factors are consistent with expectations for donors in gated nanostructures.

Demonstration of a silicon-based quantum cellular automata cell

We report on the demonstration of a silicon-based quantum cellular automata (QCA) unit cell incorporating two pairs of metallically doped (n+) phosphorus-implanted nanoscale dots, separated from source and drain reservoirs by nominally undoped tunnel barriers. Metallic cell control gates, together with Al–AlOx single electron transistors for noninvasive cell-state readout, are located on the device surface and capacitively coupled to the buried QCA cell. Operation at subkelvin temperatures was demonstrated by switching of a single electron between output dots, induced by a driven single electron transfer in the input dots. The stability limits of the QCA cell operation were also determined.

Imaging with ionoluminescence (IL) in a nuclear microprobe

Abstract A system for the detection of luminescence induced by a 2.5 MeV proton beam (ionoluminescence; IL) to be used in combination with a nuclear microprobe is described. Results of IL imaging are compared with X-ray and secondary electron maps acquired simultaneously. Beam damage is investigated by panchromatic IL imaging and IL yield decay. An IL wavelength dispersive study has also been done with the presently rather simple system. Limitations of the IL technique as well as development plans for an upgraded IL analytical facility are discussed.

Ion-beam-induced-charge characterisation of particle detectors

Abstract Ion-beam-induced-charge collection (IBIC) in a nuclear microprobe has been used to characterise detectors for the measurement of particles over a median energy range (100 keV–1 MeV). Three standard detector devices have been studied: a PIPS detector with a buried (ion-implanted) junction structure, a Schottky barrier junction device and a PN-junction photodiode. A 2.0 MeV focussed helium ion beam was used to probe the active area of each device with a spatial resolution ∼1–2 μm, to quantify the thickness of the dead layer, the charge collection response and the reduction in charge collection efficiency induced by ion-beam damage.

Drain current modulation in a nanoscale field-effect-transistor channel by single dopant implantation

We demonstrate single dopant implantation into the channel of a silicon nanoscale metal-oxide-semiconductor field-effect-transistor. This is achieved by monitoring the drain current modulation during ion irradiation. Deterministic doping is crucial for overcoming dopant number variability in present nanoscale devices and for exploiting single atom degrees of freedom. The two main ion stopping processes that induce drain current modulation are examined. We employ 500 keV He ions, in which electronic stopping is dominant, leading to discrete increases in drain current and 14 keV P dopants for which nuclear stopping is dominant leading to discrete decreases in drain current.

New problems in nuclear microprobe analysis of materials

Abstract Advanced materials are being evaluated for use as novel radiation detectors and microelectronic devices, including, potentially, synthetic diamond radiation-hard detectors for high-energy physics experiments and tissue equivalent dosimeters. Use of a nuclear microprobe has allowed spatially resolved electrical properties of the detector material to be measured. However quantitative analysis requires good models for charge collection mechanisms by ion beam induced charge (IBIC). In fact, nuclear microprobe analysis is playing an increasingly prominent role in the analysis of detector materials and devices by IBIC, with secondary roles also being played by ionoluminescence (IL) and the traditional techniques of Rutherford backscattering and particle induced X-ray emission. In this paper, many recent applications are reviewed and some examples of applications of the nuclear microprobe to the study of new materials and devices are presented. Some of these applications involve wide band gap materials, such as GaN, as well as novel detectors for radiation dosimetry in cancer therapy, photovoltaic devices and other microelectronic devices.

Electron tunnel rates in a donor-silicon single electron transistor hybrid

We investigate a hybrid structure consisting of a small number of implanted

Ion implanted Si:P double dot with gate tunable interdot coupling

^{31}\text{P}

Single-Ion Implantation for the Development of Si-Based MOSFET Devices with Quantum Functionalities

atoms close to a gate-induced silicon single electron transistor (SiSET). In this configuration, the SiSET is extremely sensitive to the charge state of the nearby centers, turning from the off state to the conducting state when the charge configuration is changed. We present a method to measure fast electron tunnel rates between donors and the SiSET island, using a pulsed voltage scheme and low-bandwidth current detection. The experimental findings are quantitatively discussed using a rate equation model, enabling the extraction of the capture and emission rates.