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Amorphous boron-carbon-nitrogen (B-C-N) films with low density are potentially interesting as alternative low-dielectric-constant (low-kappa) materials for future electronic devices. Such applications require deposition at temperatures below 300 degrees C, making plasma chemical vapor deposition (plasma CVD) a preferred deposition method. Plasma CVD of B-C-N films is today typically done with separate precursors for B, C and N or with precursors containing B-N bonds and an additional carbon precursor. We present an approach to plasma CVD of B-C-N films based on triethylboron (B(C2H5)(3)), a precursor with B-C bonds, in an argon-nitrogen plasma. From quantitative analysis with time-of-flight elastic recoil detection analysis (ToF-ERDA), we find that the deposition process can afford B-C-N films with a B/N ratio between 0.9-1.3 and B/C ratios between 3.4-8.6 and where the films contain from 3.6 to 7.8 at% H and from 6.6 to 20 at% O. The films have low density, from 0.32 to 1.6 g cm(-3) as determined from cross-section scanning electron micrographs and ToF-ERDA with morphologies ranging from smooth films to separated nanowalls. Scanning transmission electron microscopy shows that C and BN do not phase-separate in the film. The static dielectric constant kappa, measured by capacitance-voltage measurements, varies with the Ar concentration in the range from 3.3 to 35 for low and high Ar concentrations, respectively. We suggest that this dependence is caused by the energetic bombardment of plasma species during film deposition. ; Funding Agencies|Swedish Foundation for Strategic Research (SSF)Swedish Foundation for Strategic Research [IS14-0027]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University [2009-00971]; Swedish research council VR-RFISwedish Research Council [2017-00646_9]; Swedish Foundation for Strategic ResearchSwedish Foundation for Strategic Research [RIF14-0053]; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation

Epitaxial rhombohedral boron nitride (r-BN) films were deposited on ZrB2(0001)/4H-SiC(0001) by chemical vapor deposition at 1485 degrees C from the reaction of triethylboron and ammonia and with a minute amount of silane (SiH4). X-ray diffraction (XRD) w-scans yield the epitaxial relationships of r-BN(0001) k ZrB2(0001) out-of-plane and r-BN[11-20] k ZrB2[11-20] in-plane. Cross-sectional transmission electron microscopy (TEM) micrographs showed that epitaxial growth of r-BN films prevails to similar to 10 nm. Both XRD and TEM demonstrate the formation of carbon- and nitrogen-containing cubic inclusions at the ZrB2 surface. Quantitative analysis from x-ray photoelectron spectroscopy of the r-BN films shows B/N ratios between 1.30 and 1.20 and an O content of 3-4 at. %. Plan-view scanning electron microscopy images reveal a surface morphology where an amorphous material comprising B, C, and N is surrounding the epitaxial twinned r-BN crystals. ; Funding Agencies|Swedish Foundation for Strategic Research (SSF)Swedish Foundation for Strategic Research [IS14-0027]; Carl Tryggers Foundation for Scientific Research [CTS 14:189]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]

In the present communication, the atomic structure and coordination of surface adsorbed species on Nb2C MXene is investigated over time. In particular, the influence of the Nb adatoms on the structural stability and oxidation behavior of the MXene is addressed. This investigation is based on plan-view geometry observations of single Nb2C MXene sheets by a combination of atomic-resolution scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and STEM image simulations. ; Funding agencies:The authors acknowledge the Swedish Research Council for funding under grants no. 2016- 04412 and 642-2013-8020, the Knut and Alice Wallenberg's Foundation for support of the electron microscopy laboratory in Linköping, a Fellowship grant and a project grant (KAW 2015.0043). The authors also acknowledge Swedish Foundation for Strategic Research (SSF) through the Research Infrastructure Fellow program no. RIF 14-0074. The authors finally acknowledge support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No 2009 00971

The spinodal decomposition and thermal stability of thin In0.72Al0.28N layers and In0.72Al0.28N/AlN superlattices with AlN(0001) templates on Al2O3(0001) substrates was investigated by in-situ heating up to 900 degrees C. The thermally activated structural and chemical evolution was investigated in both plan-view and cross-sectional geometries by scanning transmission electron microscopy in combination with valence electron energy loss spectroscopy. The plan-view observations demonstrate evidence for spinodal decomposition of metastable In0.72Al0.28N after heating at 600 degrees C for 1 h. During heating compositional modulations in the range of 2-3 nm-size domains are formed, which coarsen with applied thermal budgets. Cross-sectional observations reveal that spinodal decomposition begin at interfaces and column boundaries, indicating that the spinodal decomposition has a surface-directed component. ; Funding Agencies|Swedish Research Council (VR) [621-2012-4420, 621-2012-4359, 622-2008-405]; European Research Council (ERC); Swedish Foundation for Strategic research (SSF) through the Nano-N program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; Knut and Alice Wallenberg Foundation

All atomically laminated MAB phases (M = transition metal, A = A-group element, and B = boron) exhibit orthorhombic or tetragonal symmetry, with the only exception being hexagonal Ti2InB2. Inspired by the recent discovery of chemically ordered hexagonal carbides, i-MAX phases, we perform an extensive first-principles study to explore chemical ordering upon metal alloying of M2AlB2 (M from groups 3 to 9) in orthorhombic and hexagonal symmetry. Fifteen stable novel phases with in-plane chemical ordering are identified, coined i-MAB, along with 16 disordered stable alloys. The predictions are verified through the powder synthesis of Mo4/3Y2/3 AlB2 and Mo4/3Sc2/3AlB2 of space group R (3) over barm (no. 166), displaying the characteristic in-plane chemical order of Mo and Y/Sc and Kagome ordering of the Al atoms, as evident from X-ray diffraction and electron microscopy. The discovery of i-MAB phases expands the elemental space of these borides with M = Sc, Y, Zr, Hf, and Nb, realizing an increased property tuning potential of these phases as well as their suggested potential twodimensional derivatives. ; Funding Agencies|Knut and Alice Wallenberg (KAW) FoundationKnut & Alice Wallenberg Foundation [KAW 2015.0043]; Swedish Foundation for Strategic Research (SSF)Swedish Foundation for Strategic Research [EM16-0004]; Swedish Research councilSwedish Research Council [2019-05047, 201904233, 2016-04412]; Swedish Foundation for Strategic Research (SSF) through the Research Infrastructure Fellow Program [RIF 14-0074]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

Zirconium diboride (ZrB2) films have been deposited by direct current magnetron sputtering (DCMS) from a ZrB2 compound target on Al2O3 (0001) substrates held at 600, 700, 800, and 900 degrees C, and with two different axial magnetic field strengths, 34 and 104 G, generated using a coil surrounding the substrate. Plasma probe measurements show an increase of the ion fluxes on floating-potential substrates of the two different configurations by a factor of 2.8 for 104 G compared to 34 G, while the ion energy remained relatively constant at approximate to 12 eV. Time-of-flight elastic recoil detection analysis (ToF-ERDA) show that films deposited with a magnetic field of 34 G are highly overstoichiometric with B/Zr ratios approximate to 2.4, while films deposited with 104 G exhibit a B/Zr ratios approximate to 2.1. The levels of oxygen and carbon in the films are below 1 at. % irrespective of growth conditions. X-ray diffraction (XRD) 0/20 scans, complemented by pole figure measurements, reveal that all deposited films are 0001-oriented. XRD 0/20 scans of the 000t peak intensities and co (rocking-curve) widths show increased ZrB2 crystal quality with increasing temperature for both magnetic field strengths. Minimum electrical resistivity of approximate to 100 p omega cm is achieved for an axial magnetic field of 104 G, independent of temperature. ; Funding Agencies|Knut and Alice Wallenberg Foundation, Project Grant (The Boride Frontier) [KAW 2015.0043]; electron microscopy laboratory in Linkoping; Aforsk Foundation [16-430]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Swedish research council VR-RFISwedish Research Council [2017-00646_9]; Swedish Foundation for Strategic ResearchSwedish Foundation for Strategic Research [RIF14-0053]

Recently, we presented a family of in-plane chemically ordered transition metal borides of the general formula (M-2/3M-1/3")(2)AlB2. Here, we investigate incorporation of magnetic rare earth (RE) elements into this structure by synthesis and analysis of Mo4/3RE2/3AlB2, where RE = Ho, Tb, and Er. The crystal structure is verified by X-ray diffraction and scanning transmission electron microscopy, while the composition is derived from energy dispersive X-ray analysis. Through magnetization measurements, we also show that Mo4/3Ho2/3AlB2 orders antiferromagnetically below 9 K. We suggest that (M-2/3M-1/3")(2)AlB2 could potentially be a versatile platform for new magnetic materials, in 3D as well as 2D. [GARPHICS] IMPACT STATEMENT This paper introduces magnetic elements to i-MAB phases family with a formula of Mo4/3RE2/3AlB2 (RE = Ho, Er, and Tb), which opens a venue for further exploration of chemically ordered magnetic materials. ; Funding Agencies|Knut and Alice Wallenberg (KAW) FoundationKnut & Alice Wallenberg Foundation [KAW 2020.0033]; Swedish Research councilSwedish Research CouncilEuropean Commission [2021-00471, 2019-04233]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

Selective-area grown, catalyst-free GaN nanorod (NR) arrays grown on Si substrates have been realized using liquid-target reactive magnetron sputter epitaxy (MSE). Focused ion beam lithography (FIBL) was applied to pattern Si substrates with TiN(x)masks. A liquid Ga target was sputtered in a mixture gas of Ar and N-2, ranging the N(2)partial pressure (P-N) ratio from 100% to 50%. The growth of NRs shows a strong correlation withP(N)on the selectivity, coalescence, and growth rate of NRs in both radial and axial directions. The growth rate of NRs formed inside the nanoholes increases monotonically withP(N). TheP(N)ratio between 80% and 90% was found to render both a high growth rate and high selectivity. When theP(N)ratio was below 80%, multiple NRs were formed in the nanoholes. For aP(N)ratio higher than 90%, parasitic NRs were grown on the mask. An observed dependence of growth behavior upon theP(N)ratio is attributed to a change in the effective Ga/N ratio on the substrate surface, as an effect of impinging reactive species, surface diffusivity, and residence time of adatoms. The mechanism of NR growth control was further investigated by studying the effect of nanoholes array pitch and growth temperature. The surface diffusion and the direct impingement of adatoms were found to be the dominant factors affecting the lateral and axial growth rates of NR, respectively, which were well elucidated by the collection area model. ; Funding Agencies|Energimyndigheten [46658-1]; VetenskapsradetSwedish Research Council [2018-04198]; Stiftelsen Olle Engkvist ByggmastareSwedish Research Council [197-0210]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; Energimyndigheten

Catalyst-free GaN nanorod regular arrays have been realized by reactive magnetron sputter epitaxy. Two nanolithographic methods, nanosphere lithography (NSL) and focused ion beam lithography (FIBL), were applied to pattern Si substrates with TiNx masks. The growth temperature was optimized for achieving selectivity and well-faceted nanorods grown onto the NSL-patterned substrates. With increasing temperature from 875 to 985 °C, we observe different growth behaviors and associate them with selective insensitive, diffusion-dominated, and desorption-dominated zones. To further achieve site-specific and diameter control, these growth parameters were transferred onto FIBL-patterned substrates. Further investigation into the FIBL process through tailoring of milling current and time in combination with varying nanorod growth temperature, suggests that minimization of mask and substrate damage is the key to attain uniform, well-defined, single, and straight nanorods. Destruction of the mask results in selective area growth failure, while damage of the substrate surface promotes inclined nanorods grown into the openings, owning to random oriented nucleation. ; Funding agencies: Swedish Research Council (VR) [621-2012-4420, 621-2013-5360, 2016-04412]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program; Swedish Foundation for Strategic Research (SSF) [RIF 14-0074]; Sw

A vacancy-ordered MXene, Mo1.33CTz, obtained from the selective etching of Al and Sc from the parent i-MAX phase (Mo2/3Sc1/3)(2)AlC has previously shown excellent properties for supercapacitor applications. Attempts to synthesize the same MXene from another precursor, (Mo2/3Y1/3)(2)AlC, have not been able to match its forerunner. Herein, we show that the use of an AlY2.3 alloy instead of elemental Al and Y for the synthesis of (Mo2/3Y1/3)(2)AlC i-MAX, results in a close to 70% increase in sample purity due to the suppression of the main secondary phase, Mo3Al2C. Furthermore, through a modified etching procedure, we obtain a Mo1.33CTz MXene of high structural quality and improve the yield by a factor of 6 compared to our previous efforts. Free-standing films show high volumetric (1308 F cm(-3)) and gravimetric (436 F g(-1)) capacitances and a high stability (98% retention) at the level of, or even beyond, those reported for the Mo1.33CTz MXene produced from the Sc-based i-MAX. These results are of importance for the realization of high quality MXenes through use of more abundant elements (Y vs. Sc), while also reducing waste (impurity) material and facilitating the synthesis of a high-performance material for applications. ; Funding Agencies|Knut and Alice Wallenberg (KAW) FoundationKnut & Alice Wallenberg Foundation; Swedish Foundation for Strategic Research (SSF)Swedish Foundation for Strategic Research [EM16-0004]; KAW Foundation; Swedish Research CouncilSwedish Research Council [2016-04412]; Swedish Foundation for Strategic Research (SSF) through the Research Infrastructure Fellow program [RIF 14-0074]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

We report the synthesis and characterization of a new laminated i-MAX phase, (V2/3Sc1/3)(2)AlC, with in-plane chemical ordering between the M-elements. We also present evidence for the solid solution (V2-xScx)(2)AlC, where x amp;lt;= 0.05. Chemical etching of the Al and Sc results in a two-dimensional (2D) MXene counterpart: V2-xC from the latter phase. Furthermore, etching with HF yields single-sheet MXene of flat morphology, while LiF + HCl gives MXene scrolls. We also show a 4x reduction in etching time for (V2-xScx)(2)AlC compared to V2AlC, suggesting that traces of Sc changes the phase stability, and make the material more susceptible to etching. The results show a path for improved control of MXene synthesis and morphology, which may be applicable also for other MAX/MXene systems. ; Funding Agencies|Swedish Foundation for Strategic Research (SSF)Swedish Foundation for Strategic Research [EM16-0004]; Research Infrastructure Fellow program [RIF 14-0074]; Knut and Alice Wallenberg (KAW) FoundationKnut & Alice Wallenberg Foundation; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Swedish Research councilSwedish Research Council [642-2013-8020, 2016-04412]; [KAW 2015.0043]

Nanostructure formation via surface-diffusion-mediated segregation of ZrN and AIN in Zr1-xAlxN films during high mobility growth conditions is investigated for 0 amp;lt;= x amp;lt;= 1. The large immiscibility combined with interfacial surface and strain energy balance resulted in a hard nanolabyrinthine lamellar structure with well-defined (semi) coherent c-ZrN and w-AlN domains of sub-nm to similar to 4 nm in 0.2 amp;lt;= x amp;lt;= 0.4 films, as controlled by atom mobility. For high AlN contents (x amp;gt; 0.49) Al-rich ZrN domains attain wurtzite structure within fine equiaxed nanocomposite wurtzite lattice. Slow diffusion in wurtzite films points towards crystal structure dependent driving force for decomposition. The findings of unlikelihood of isostructural decomposition in c-Zr1-xAlxN, and stability of w-Zr1-xAlxN (in large x films) is complemented with first principles calculations. ; Funding Agencies|Swedish Governmental Agency for Innovation Systems (Vinnova) through the VINNMER Grant [2011-03464]; Knut and Wallenberg Foundation

This review celebrates the width and depth of electron microscopy methods and how these have enabled massive research efforts on MXenes. MXenes constitute a powerful recent addition to 2-dimensional materials, derived from their parent family of nanolaminated materials known as MAX phases. Owing to their rich chemistry, MXenes exhibit properties that have revolutionized ranges of applications, including energy storage, electromagnetic interference shielding, water filtering, sensors, and catalysis. Few other methods have been more essential in MXene research and development of corresponding applications, compared with electron microscopy, which enables structural and chemical identification at the atomic scale. In the following, the electron microscopy methods that have been applied to MXene and MAX phase precursor research are presented together with research examples and are discussed with respect to advantages and challenges. ; Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [2016-04412]; Knut and Alice Wallenbergs FoundationKnut & Alice Wallenberg Foundation [KAW 2015.0043]; Swedish Foundation for Strategic Research (SSF) through the Research Infrastructure Fellow program [RIF 14-0074]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Link_oping University [2009 00971]

Magnetron sputter deposition of TiBx thin films from a TiB2 target typically results in highly overstoichiometric films due to differences in sputtered-atom ejection angles and gas-phase scattering during transport to the substrate. This study investigates the effects of the magnetron magnetic field strength at the substrate position and the Ar sputtering pressure on the resulting film composition and crystalline quality. It is shown that the B/Ti atomic ratio can be reduced from 2.7 to 2.1 by increasing the Ar pressure from 5 mTorr to 20 mTorr, a trend consistent with previous work. Despite the use of a relatively high Ar pressure, a change to a stronger outer magnetic pole leads to, dense TiB2.1 films of high crystal quality, as shown by X-ray diffraction, scanning transmission electron microscopy, and specific resistivity of 32 mu Omega cm. For epitaxial films deposited at 900 degrees C on Al2O3(001), a TiB2[110]//Al2O3[100] orientational relationship were obtained. ; Funding Agencies|Knut and Alice Wallenberg (KAW) FoundationKnut & Alice Wallenberg Foundation [KAW 2015.0043]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Link_oping University [2009 00971]; VR-RFI (Vetenskapsradet) [821-2012-5144]; Swedish Foundation for Strategic ResearchSwedish Foundation for Strategic Research [SSF, RIF14-0053]