The microwave cavity perturbation (MCP) technique is used to identify the transition from magnetite (Fe3O4) meta-stable form of maghemite (γ-Fe2O3). In this study Fe3O4 was annealed at temperatures 60 300 °C vary oxidation. Subsequent annealing, complex permittivity and magnetic permeability iron oxide powders were measured. γ-Fe2O3 corroborated with x-ray diffraction (XRD), photoelectron spectroscopy (XPS) vibrating sample magnetometry (VSM). XRD, XPS VSM implied that starting powder...

The growth of >100-μm-thick diamond layers adherent on aluminum nitride with low thermal boundary resistance between and AlN is presented in this work. barrier was found to be the range 16 m2·K/GW, which a large improvement current state-of-the-art. While thick films failed adhere untreated films, treated hydrogen/nitrogen plasma retained layers. Clear differences ζ-potential measurement confirm surface modification due treatment. An increase non-diamond carbon initial grown pretreated seen...

Integrating diamond with GaN high electron mobility transistors (HEMTs) improves thermal management, ultimately increasing the reliability and performance of high-power high-frequency radio frequency amplifiers. Conventionally, an amorphous interlayer is used before growing polycrystalline onto in these devices. This layer contributes significantly to effective boundary resistance (TBReff) between HEMT diamond, reducing benefit heat spreader. Replacing a higher conductivity crystalline...

Diamond heat-spreaders for gallium nitride (GaN) devices currently depend upon a robust wafer bonding process. Bonding-free membrane methods demonstrate potential, however, chemical vapour deposition (CVD) of diamond directly onto III-nitride (III–N) heterostructure induces significant thermal stresses. In this work, these stresses are investigated using an analytical approach, numerical model and experimental validation. The caused by the mismatch in coefficient expansion (CTE) between...

In this work a strategy to grow diamond on $β$-Ga$_2$O$_3$ has been presented. The $ζ$-potential of the substrate was measured and it found be negative with an isoelectric point at pH $\sim$ 4.6. substrates were seeded mono-dispersed solution for growth diamond. etched when exposed plasma globules gallium could seen surface. To overcome problem $\sim$100 nm SiO$_2$ Al$_2$O$_3$ deposited using atomic layer deposition. nanodiamond effective in protecting thin layers grown. contrast damaged...

A microwave plasma model of a chemical vapour deposition (CVD) reactor is presented for understanding spatial heteroepitaxial growth polycrystalline diamond on Si. This work based the TM0(n>1) clamshell style (Seki Diamond/ASTEX SDS 6K, Carat CTS6U, ARDIS-100 style) whereby simplified H2 used to show radial variation in rate over small samples with different sample holders. The uses several steps: an electromagnetic (EM) eigenfrequency solution, frequency-transient EM/plasma fluid solution...

The quality of polycrystalline diamond films is heavily dependent on the nucleation and early stages growth, making ability to monitor these highly desirable. Spectroscopic ellipsometry (SE) allows for real-time monitoring thickness, composition, morphology with sub-nanometre precision. In this work, ex-situ SE spectra were used develop an optical model film characterisation, which was then applied in-situ data. coalescence individual crystallites into a single observed through parabolic...

GaN high electron mobility transistors (HEMTs) on SiC substrates are the highest performing commercially available for high-power, high-frequency applications. However, Joule self-heating limits maximum areal power density, i.e., operating is derated to ensure lifetime of GaN-based devices. Diamond attractive as a heat sink due its record-high thermal conductivity combined with electrical resistivity. GaN-on-diamond devices have been demonstrated, bringing diamond close possible active...

GaN-on-diamond samples were demonstrated using a membrane-based technology. This was achieved by selective area Si substrate removal of areas up to 1 cm × from GaN-on-Si wafer, followed direct growth polycrystalline diamond microwave plasma chemical vapor deposition on etch exposed N-polar AlN epitaxial nucleation layers. Atomic force microscopy and transmission electron used confirm the formation high quality, void-free AlN/diamond interfaces. The bond between III-nitride layers validated...

This work presents an easy-to-use microwave split dielectric resonator (MSDR) for X-band measurements of free-standing unpolished poly-crystalline diamond (PCD). PCD grown with varying CH4/H2 and O2/ in the gas phase show stark differences loss. Low loss is found concentrations less than 5% while O2 very high tangents. Vacuum annealing introduces non-diamond carbon (NDC) impurities which increases loss, however, even after significant discolouration still lower PCD. The mechanism likely due...

In this paper we have used laser powder bed fusion (PBF) to manufacture and characterize metal microwave components. Here focus on a 2.5 GHz cavity resonator, manufactured by PBF from the alloy AlSi10Mg. Of particular interest is its thermal expansion coefficient, especially since many applications for produced components will be in satellite systems where extreme ranges of temperature are experienced. We exploit inherent resonant frequency dependence geometry, using number TM modes,...

Broadband microwave complex permittivity measurements of nanodiamond powders are presented. Previous studies show that dielectric loss strongly correlate with the presence nondiamond surface impurities. In this study, frequency dependence these losses is investigated using cavity perturbation (MCP) and broadband coaxial probe (BCP) methods. This allowed further understanding as to what mechanisms contribute absorption (free electron conduction or from disordered surfaces). A multimode MCP...

Non-contact and non-destructive electrical conductivity measurements of nitrogen doped nano-crystalline diamond films have been demonstrated using a microwave cavity perturbation system. The the was controlled by simply varying CH4 gas concentration during plasma assisted chemical vapour deposition, thereby promoting formation sp2 carbon at grain boundaries. presence is verified through Raman spectroscopy, x-ray photoelectron spectroscopy electron energy loss while scanning microscopy...

ConspectusThe heterogeneous integration of materials offers new paradigms in many extreme applications, where single cannot solve the problem alone. Diamond has a plethora superlative properties that make it attractive diverse array such as its unique combination unrivalled thermal conductivity combined with high electrical impedance; photon emission at room temperature; acoustic wave velocity, and Debye temperature. Most these are directly related to diamond's atomically dense lattice light...

The need for accurate material property measurements using microwave cavities requires a form of compensation to correct changes in temperature and other external influences. This paper details method correcting cavity perturbation by monitoring two modes; one which is perturbed the sample not (referred as nodal mode). modes used (TM310 TE311 an axial cylindrical cavity) are subject only sample-independent To demonstrate this technique, bulk permittivity PTFE rod has been measured under...

Additive manufactured (AM) metals are a subject of much interest for their performance in passive microwave applications. However, limitations could arise due to artifacts, such as surface texture and/or roughness resulting from the manufacturing process. We have, therefore, adopted parallel plate resonator accurate measurement resistance flat metal plates, allowing current flow two orthogonal directions by simply exciting different resonant mode (at 5.3 and 6.4 GHz), without need remove...

A superconducting boron doped nanocrystalline diamond (B-NCD) coplanar waveguide resonator (CPR) is presented for kinetic inductance ($L_k$) and penetration depth ($\lambda_{\rm{L}}$) measurements at microwave frequencies of 0.4 to 1.2 GHz temperatures below 3 K. Using a simplified effective medium CPR approach, this work demonstrates that thin granular B-NCD films ($t\approx $ 500 nm) on Si have large ($\lambda_{\rm{L}}\approx 4.3$ 4.4 $\mu$m), therefore an associated high ($L_{k,\square}...

It is important to account for variance in substrate temperature during microwave plasma-enhanced chemical vapour deposition (MPECVD) nanocrystalline diamond growth, as this has a significant impact on the uniformity of grown film. In work, an in-situ method mapping under MPECVD growth conditions demonstrated, employing mirror galvanometer scan field view dual-wavelength pyrometer across substrate. Temperature maps generated were compared plasma electron densities simulated using finite...

The high thermal conductivity of polycrystalline diamond makes it ideally suited for management solutions gallium nitride (GaN) devices, with a layer grown on an aluminum (AlN) interlayer atop the GaN stack. However, this application is limited by barrier at interface between and substrate, which has been associated transition region formed in initial phases growth. In work, situ spectroscopic ellipsometry (SE) employed to monitor early-stage microwave plasma-enhanced chemical vapor...