Single atom devices by ion implantation

Abstract

To expand the capabilities of semiconductor devices for new functions exploiting the quantum states of single donors or other impurity atoms requires a deterministic fabrication method. Ion implantation is a standard tool of the semiconductor industry and we have developed pathways to deterministic ion implantation to address this challenge. Although ion straggling limits the precision with which atoms can be positioned, for single atom devices it is possible to use post-implantation techniques to locate favourably placed atoms in devices for control and readout. However, large-scale devices will require improved precision. We examine here how the method of ion beam induced charge, already demonstrated for the deterministic ion implantation of 14 keV P donor atoms in silicon, can be used to implant a non-Poisson distribution of ions in silicon. Further, we demonstrate the method can be developed to higher precision by the incorporation of new deterministic ion implantation strategies that employ on-chip detectors with internal charge gain. In a silicon device we show a pulse height spectrum for 14 keV P ion impact that shows an internal gain of 3 that has the potential of allowing deterministic implantation of sub-14 keV P ions with reduced straggling.

Nitrogen-vacancy centers created by N+ ion implantation through screening SiO2 layers on diamond

“…4 Being optically addressable and coherently controllable by microwaves, the single electronic spins associated with the negatively charged nitrogen-vacancy (NV − ) centers in diamond are playing important roles in emergent quantum technology, e.g., as a matter qubit interfacing with a flying qubit [5][6][7][8] and as a nanoscale magnetic sensor.…”

Quantum information density scaling and qubit operation time constraints of CMOS silicon-based quantum computer architectures

“…61,62 In brief, single electron spin donor qubits exhibit very long coherence time of the order of seconds, 44,63 and the effectiveness of atomic resolution lithography based on scanning tunneling microscope 64 is progressively approaching serial implantation. 65 The less accurate single ion implantation [66][67][68] method could achieve sufficient precision for some architecture such as a surface code implementation based on a twodimensional array of distant donors, 69 which tolerates deviation of up to 11 nm from the ideal lattice position. However, the complexity of the serial design of devices involving either individual donors with single spins for qubits with microwave control or pair of donors with two or three electrons bound to donors controlled by gates that depends on a relatively high number of currently unaddressed assumptions including yield of implantation and activation of all the donor sites, control of interdonor distance at single lattice precision, global or individual microwave control, S-T and exchange-only three spin qubits, CMOS mask design on top of silicon overgrowth on the donor layer.…”

A computational workflow for designing silicon donor qubits

“…Several works that followed the Kane proposal have also outlined how to realize qubits using the unpaired donor-bound electron, opening up the potential for easier addressability and faster gate operation [10,[18][19][20]. Recent experiments using isotopically purified 28 Si have demonstrated single-qubit coherence times (T 2 ) over 30 s (nuclear spin) and 0.5 s (electron spin) at cryogenic temperatures [9].…”

“…Uncertainty in the position of the donor atoms therefore leads to unpredictable exchange couplings. Given the variability in the placement of the donors [28], the external potential must be tuned sufficiently to obtain the desired value of J. In addition, the donor position needs to be well-defined relative to the surface electrodes that lie along an atomically rough boundary.…”

“…But this challenge is not insurmountable as evidenced by increasing precision in sample fabrication [30], reduced decoherence from isotopic purification of the silicon substrate, and recent efforts to directly visualize the donor electronic state [31]. Very recently, Laucht et alrealized a single-qubit device from a lone 31 P atom embedded in isotopically pure 28 Si [25]. In particular, the electron and nuclear spin states of the P donor were manipulated using nanoscale gates to perform single-qubit logic gates and measure experimental signatures of coherence.…”