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Christopher I. Pakes

Publications and source records attributed to Christopher I. Pakes.

5 recordsLinked to original sources
arXiv2026

High-field Magnetotransport Studies of Surface Conducting Diamonds

The observation of strong and tunable spin-orbit interaction (SOI) in surface conducting diamond opens up a new avenue for building diamond-based spintronics. Herein we provide a comprehensive method to analyze the magnetotransport behavior of surface conducting hydrogen-terminated diamond (H-diamond) Hall bar devices and Al/Al2O3/V2O5/H-diamond MOSFETs, respectively. By adopting a significantly improved theoretical magneto transport model, the reduced magnetoconductance can be accurately explained both within and outside the quantum diffusive regime. The model is valid for all doping strategies of surface conducting diamond tested. From this analysis, we find that the orbital magnetoresistance, a classical effect distinct from the SOI, dominates the magnetotransport in surface conducting diamond at high magnetic fields. Furthermore, local hole mobilities as high as 1000 ~ 3000 cm2/Vs have been observed in this work, indicating the possibility of diamond-based electronics with ultra-high hole mobilities at cryogenic temperatures.

cond-mat.mtrl-sci↗
arXiv2026

Tunneling probe-based identification of the sp${}^3$ dangling bond on the H-C(100):$2\times1$ surface

The sp${}^3$ dangling bond on the diamond surface plays a critical role in the performance and fabrication of diamond quantum technologies. For the former, the magnetic and electric properties of this defect can impede the performance of quantum sensors and computers. For the latter, the chemical properties of the dangling bond are integral to proposed methods for bottom-up fabrication of scalable diamond quantum devices. In pursuit of high performance and scalable diamond quantum technology, tunneling probe-based techniques offers the ability to create and modify the sp${}^3$ dangling bond with atomic-scale precision. However, these capabilities cannot be realised either deterministically or at scale without a means for identifying the sp${}^3$ dangling bond amidst the myriad of other defects on the diamond surface. Consequently, in this work we provide a comprehensive experimental and theoretical framework for STS-based characterisation of the sp${}^3$ defect on the H-terminated (100) diamond surface. This capability provides the foundation for future tunneling probe studies in the modification of dangling bonds.

cond-mat.mes-hall↗
arXiv2024

Identification of defects and the origins of surface noise on hydrogen-terminated (100) diamond

Near-surface nitrogen-vacancy centres are critical to many diamond-based quantum technologies such as information processors and nanosensors. Surface defects play an important role in the design and performance of these devices. The targeted creation of defects is central to proposed bottom-up approaches to nanofabrication of quantum diamond processors, and uncontrolled surface defects may generate noise and charge trapping which degrade shallow NV device performance. Surface preparation protocols may be able to control the production of desired defects and eliminate unwanted defects, but only if their atomic structure can first be conclusively identified. This work uses a combination of scanning tunnelling microscopy (STM) imaging and first-principles simulations to identify several surface defects on H:C(100)-2x1 surfaces prepared using chemical vapour deposition (CVD). The atomic structure of these defects is elucidated, from which the microscopic origins of magnetic noise and charge trapping is determined based on modelling of their paramagnetic properties and acceptor states. Rudimentary control of these deleterious properties is demonstrated through STM tip-induced manipulation of the defect structure. Furthermore, the results validate accepted models for CVD diamond growth by identifying key adsorbates responsible for nucleation of new layers.

cond-mat.mes-hall↗
arXiv2010

Flux noise in ion-implanted nanoSQUIDs

Focused ion beam (FIB) technology has been used to fabricate miniature Nb DC SQUIDs which incorporate resistively-shunted microbridge junctions and a central loop with a hole diameter ranging from 1058 nm to 50 nm. The smallest device, with a 50 nm hole diameter, has a white flux noise level of 2.6 microphy_{0}/Hz^{0.5} at 10^{4} Hz. The scaling of the flux noise properties and focusing effect of the SQUID with the hole size were examined. The observed low-frequency flux noise of different devices were compared with the contribution due to the spin fluctuation of defects during FIB processing and the thermally activated flux hopping in the SQUID washer.

cond-mat.supr-con↗