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Register a new userEffect of Low-Damage Inductively Coupled Plasma on Shallow NV Centers in Diamond
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Added by
Felipe Favaro De Oliveira
Publication date
2015
fields
Physics
and research's language is
English
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Near-surface nitrogen-vacancy ({NV}) centers in diamond have been successfully employed as atomic-sized magnetic field sensors for external spins over the last years. A key challenge is still to develop a method to bring NV centers at nanometer proximity to the diamond surface while preserving their optical and spin properties. To that aim we present a method of controlled diamond etching with nanometric precision using an oxygen inductively coupled plasma (ICP) process. Importantly, no traces of plasma-induced damages to the etched surface could be detected by X-ray photoelectron spectroscopy (XPS) and confocal photoluminescence microscopy techniques. In addition, by profiling the depth of NV centers created by 5.0 keV of nitrogen implantation energy, no plasma-induced quenching in their fluorescence could be observed. Moreover, the developed etching process allowed even the channeling tail in their depth distribution to be resolved. Furthermore, treating a 12C isotopically purified diamond revealed a threefold increase in T2 times for NV centers with <4 nm of depth (measured by NMR signal from protons at the diamond surface) in comparison to the initial oxygen-terminated surface.
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Creation of nitrogen-vacancy (NV) centers at the nanoscale surface region in diamond, while retaining their excellent spin and optical properties, is essential for applications in quantum technology. Here, we demonstrate the extension of the spin-coherence time ($it{T}$${_2}$), the stabilization of the charge state, and an improvement of the creation yield of NV centers formed by the ion-implantation technique at a depth of $sim$15 nm in phosphorus-doped n-type diamond. The longest $it{T}$${_2}$ of about 580 $mu$s of a shallow NV center approaches the one in bulk diamond limited by the nuclear spins of natural abundant $^{13}$C. The averaged $it{T}$${_2}$ in n-type diamond is over 1.7 times longer than that in pure non-doped diamond. Moreover, the stabilization of the charge state and the more than twofold improvement of the creation yield are confirmed. The enhancements for the shallow NV centers in an n-type diamond-semiconductor are significant for future integrated quantum devices.
We investigate the influence of plasma treatments, especially a 0V-bias, potentially low damage O$_2$ plasma as well as a biased Ar/SF$_6$/O$_2$ plasma on shallow, negative nitrogen vacancy (NV$^-$) centers. We ignite and sustain using our 0V-bias plasma using purely inductive coupling. To this end, we pre-treat surfaces of high purity chemical vapor deposited single-crystal diamond (SCD). Subsequently, we create $sim$10 nm deep NV$^-$ centers via implantation and annealing. Onto the annealed SCD surface, we fabricate nanopillar structures that efficiently waveguide the photoluminescence (PL) of shallow NV$^-$. Characterizing single NV$^-$ inside these nanopillars, we find that the Ar/SF$_6$/O$_2$ plasma treatment quenches NV$^-$ PL even considering that the annealing and cleaning steps following ion implantation remove any surface termination. In contrast, for our 0V-bias as well as biased O$_2$ plasma, we observe stable NV$^-$ PL and low background fluorescence from the photonic nanostructures.
We investigate the magnetic field dependent photo-physics of individual Nitrogen-Vacancy (NV) color centers in diamond under cryogenic conditions. At distinct magnetic fields, we observe significant reductions in the NV photoluminescence rate, which indicate a marked decrease in the optical readout efficiency of the NVs ground state spin. We assign these dips to excited state level anti-crossings, which occur at magnetic fields that strongly depend on the effective, local strain environment of the NV center. Our results offer new insights into the structure of the NVs excited states and a new tool for their effective characterization. Using this tool, we observe strong indications for strain-dependent variations of the NVs orbital g-factor, obtain new insights into NV charge state dynamics, and draw important conclusions regarding the applicability of NV centers for low-temperature quantum sensing.
Nonradiative transfer processes are often regarded as loss channels for an optical emitter1, since they are inherently difficult to be experimentally accessed. Recently, it has been shown that emitters, such as fluorophores and nitrogen vacancy centers in diamond, can exhibit a strong nonradiative energy transfer to graphene. So far, the energy of the transferred electronic excitations has been considered to be lost within the electron bath of the graphene. Here, we demonstrate that the trans-ferred excitations can be read-out by detecting corresponding currents with picosecond time resolution. We electrically detect the spin of nitrogen vacancy centers in diamond electronically and con-trol the nonradiative transfer to graphene by electron spin resonance. Our results open the avenue for incorporating nitrogen vacancy centers as spin qubits into ultrafast electronic circuits and for harvesting non-radiative transfer processes electronically.
We present an enhancement of spin properties of the shallow (<5nm) NV centers by using ALD to deposit titanium oxide layer on the diamond surface. With the oxide layer of an appropriate thickness, increases about 2 up to 3.5 times of both relaxation time and evolution time were achieved and the shallow NV center charge states stabilized as well. Moreover, the coherence time kept almost unchanged. This surface coating technique could produce a protective coating layer of controllable thickness without any damages to the solid quantum system surface, making it possible to prolong T1 time and T2* time, which would be a possible approach to the further packaging technique for the applicating solid quantum devices.
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