Photoionisation dynamics and ion-ion interaction of individual erbium ions in silicon nanotransistors

Erbium has been widely studied in a variety of host materials for its 1.5 m optical transition, which is compatible with fibre communication systems. Recent studies demonstrated 4.4 ms optical coherence time and 1.3 s nuclear spin coherence time with Er-doped Y2SiO5. This has stimulated the interest in building Er-based quantum memory and spin qubits with optical interface for large-scale quantum systems. This thesis focuses on the investigation of erbium ions in silicon nanotransistors for developing erbium quantum devices on the silicon platform. First, an efficient detection method for individual erbium ions is introduced. This method relies on the short laser pulse excitation and latched current signal readout. The latched signal can be reset by an off-resonance laser pulse and the latching period can be tuned by a gate voltage. This allows for adjustment of the detection speed for higher readout fidelity or faster readout speed. Based on the pulsed method, the dependence of the linewidth and signal intensity on excitation pulse length have been investigated. This allows us to understand the line shape and broadening of the spectrum under laser excitation. Finally, the higher bound of the optical lifetime was estimated based on a Markov model, and a Rabi oscillation process is simulated base on the optical Bloch equation. Then, the Zeeman effect of two coupled erbium ions was studied at high spectral resolution. The spectrum is distinctly different from that of a single Er ion as there are zero field splitting and anticrossings at multiple places. A model based on magnetic dipole-dipole interaction can match not only the Zeeman splitting slopes, but also the anti-crossings in the observed spectrum. Additionally, the potential of using single Er ions to map the electric field and strain in silicon nanotransistors has been explored. This provides a new method to characterise the electric field and strain in silicon sub-10-nanometer-node devices for optimising modern microelectronic devices

Single rare-earth ions as atomic-scale probes in ultra-scaled transistors

Continued dimensional scaling of semiconductor devices has driven information technology into vastly diverse applications. As the size of devices approaches fundamental limits, metrology techniques with nanometre resolution and three-dimensional (3D) capabilities are desired for device optimisation. For example, the performance of an ultra-scaled transistor can be strongly influenced by the local electric field and strain. Here we study the spectral response of single erbium ions to applied electric field and strain in a silicon ultra-scaled transistor. Stark shifts induced by both the overall electric field and the local charge environment are observed. Further, changes in strain smaller than $3\times 10^{-6}$ are detected, which is around two orders of magnitude more sensitive than the standard techniques used in the semiconductor industry. These results open new possibilities for non-destructive 3D mapping of the local strain and electric field in the channel of ultra-scaled transistors, using the single erbium ions as ultra-sensitive atomic probes.Comment: 10+5 pages, 4+3 figure

Single Rare-Earth Ions as Atomic-Scale Probes in Ultrascaled Transistors

Continued scaling of semiconductor devices has driven information technology into vastly diverse applications. The performance of ultrascaled transistors is strongly influenced by local electric field and strain. As the size of these devices approaches fundamental limits, it is imperative to develop characterization techniques with nanometer resolution and three-dimensional (3D) mapping capabilities for device optimization. Here, we report on the use of single erbium (Er) ions as atomic probes for the electric field and strain in a silicon ultrascaled transistor. Stark shifts on the Er3+ spectra induced by both the overall electric field and the local charge environment are observed. Changes in strain smaller than 3 × 10–6 are detected, which is around 2 orders of magnitude more sensitive than the standard techniques used in the semiconductor industry. These results open new possibilities for 3D mapping of the local strain and electric field in the channel of ultrascaled transistors.Q.Z. and J.D. acknowledge support from National Key R&D Program of China (Grant 2018YFA0306600), Anhui Initiative in Quantum Information Technologies (AHY050000), and China Postdoctoral Science Foundation (BX201700230, 2017M622001). C.Y. acknowledges support from an ARC Discovery Early Career Researcher Award (Grant DE150100791). This work was supported by the ARC Centre of Excellence for Quantum Computation and Communication Technology (Grant CE170100012) and the Discovery Project (Grant DP150103699)

Optical and Zeeman spectroscopy of individual Er ion pairs in silicon

We make the first study the optical energy level structure and interactions of pairs of single rare earth ions using a hybrid electro-optical detection method applied to Er-implanted silicon. Two examples of Er3+ pairs were identified in the optical spectrum by their characteristic energy level splitting patterns, and linear Zeeman spectra were used to characterise the sites. One pair is positively identified as two identical Er3+ ions in sites of at least C2 symmetry coupled via a large, 200 GHz Ising-like spin interaction and 1.5 GHz resonant optical interaction. Small non-Ising contributions to the spin interaction are attributed to distortion of the site measurable because of the high resolution of the single-ion measurement. The interactions are compared to previous measurements made using rare earth ensemble systems, and the application of this type of strongly coupled ion array to quantum computing is discussed.Comment: 11 pages, 5 figure

Spectral broadening of a single Er3+^{3+} ion in a Si nano-transistor

Single rare-earth ions in solids show great potential for quantum applications, including single photon emission, quantum computing, and high-precision sensing. However, homogeneous linewidths observed for single rare-earth ions are orders of magnitude larger than the sub-kilohertz linewidths observed for ensembles in bulk crystals. The spectral broadening creates a significant challenge for achieving entanglement generation and qubit operation with single rare-earth ions, so it is critical to investigate the broadening mechanisms. We report a spectral broadening study on a single Er$^{3+}$ ion in a Si nano-transistor. The Er-induced photoionisation rate is found to be an appropriate quantity to represent the optical transition probability for spectroscopic studies, and the single ion spectra display a Lorentzian lineshape at all optical powers in use. Spectral broadening is observed at relatively high optical powers and is caused by spectral diffusion on a fast time scale