We report on the use of helium ion implantation to independently control the out-of-plane lattice constant in epitaxial La 0.7 Sr 0.3 MnO 3 thin films without changing the in-plane lattice constants. The process is reversible by a vacuum anneal. Resistance and magnetization measurements show that even a small increase in the out-of-plane lattice constant of less than 1% can shift the metal-insulator transition and Curie temperatures by more than 100°C. Unlike conventional epitaxy-based strain tuning methods which are constrained not only by the Poisson effect but by the limited set of available substrates, the present study shows that strain can be independently and continuously controlled along a single axis. This permits novel control over orbital populations through Jahn-Teller effects, as shown by Monte Carlo simulations on a double-exchange model. The ability to reversibly control a single lattice parameter substantially broadens the phase space for experimental exploration of predictive models and leads to new possibilities for control over materials' functional properties. The crystal lattice is one of the most accessible degrees of freedom in materials. In complex oxides, effective control over lattice parameters not only facilitates the understanding of multiple interactions in strongly correlated systems, but also creates new phases and emergent functionalities [1][2][3][4]. Lattice engineering has played an extremely important role in attempts to design strongly correlated systems and has led to many important discoveries [1,[5][6][7][8]. Control over lattice strain in films using different substrates [9] has revealed enhanced ferroelectricity [10] and superconductivity [11], as well as induced superconductivity in otherwise nonsuperconducting compounds [12]. However, the basic nature of the broken translational symmetry in the crystal lattice also entails a rigidity against arbitrary control [13]. There is so far no experimental technique that allows one to alter the lattice parameter solely along a single crystal axis, i.e., with an effective Poisson's ratio of zero. For strain engineering in systems with a nonzero Poisson ratio, the lattice constant, and hence the electronic structure, necessarily change in all three directions, clouding the cause-effect relations between single degrees of freedom and order parameters.We demonstrate an approach using helium implantation to effectively "strain dope" the lattice along a single axis of a La 0.7 Sr 0.3 MnO 3 (LSMO) film that is epitaxially latticelocked to a substrate. The out-of-plane (c-axis) lattice constant can be modified independently of the in-plane lattice constants. The c-axis strain can be continuously manipulated, and is thus not restricted by the limited collection of substrates that dictate conventional epitaxial strain engineering. The change in materials' properties, while reversible via a high temperature anneal, is persistent even well above room temperature. No continuous external actuation is required as with transient pressure-induc...

In this study, we focus on the resolution limits for quasi 2-D single lines synthesized via focused electron-beam-induced direct-write deposition at 5 and 30 keV in a scanning electron microscope. To understand the relevant proximal broadening effects, the substrates were thicker than the beam penetration depth and we used the MeCpPt(IV)Me3 precursor under standard gas injection system conditions. It is shown by experiment and simulation how backscatter electron yields increase during the initial growth stages which broaden the single lines consistent with the backscatter range of the deposited material. By this it is shown that the beam diameter together with the evolving backscatter radius of the deposit material determines the achievable line widths even for ultrathin deposit heights in the sub-5-nm regime.

The ion beam induced nanoscale synthesis of PtCx (where x ∼ 5) using the trimethyl (methylcyclopentadienyl)platinum(IV) (MeCpPt(IV)Me3) precursor is investigated by performing Monte Carlo simulations of helium and neon ions. The helium beam leads to more lateral growth relative to the neon beam because of its larger interaction volume. The lateral growth of the nanopillars is dominated by molecules deposited via secondary electrons in both the simulations. Notably, the helium pillars are dominated by SE-I electrons whereas the neon pillars are dominated by SE-II electrons. Using a low precursor residence time of 70 μs, resulting in an equilibrium coverage of ∼4%, the neon simulation has a lower deposition efficiency (3.5%) compared to that of the helium simulation (6.5%). At larger residence time (10 ms) and consequently larger equilibrium coverage (85%) the deposition efficiencies of helium and neon increased to 49% and 21%, respectively; which is dominated by increased lateral growth rates leading to broader pillars. The nanoscale growth is further studied by varying the ion beam diameter at 10 ms precursor residence time. The study shows that total SE yield decreases with increasing beam diameters for both the ion types. However, helium has the larger SE yield as compared to that of neon in both the low and high precursor residence time, and thus pillars are wider in all the simulations studied.

Focused helium and neon ion beam induced etching for advanced extreme ultraviolet lithography mask repair.

A Monte Carlo simulation is developed to model the physical sputtering of aluminum and tungsten emulating nanoscale focused helium and neon ion beam etching from the gas field ion microscope. Neon beams with different beam energies (0.5-30 keV) and a constant beam diameter (Gaussian with full-width-at-half-maximum of 1 nm) were simulated to elucidate the nanostructure evolution during the physical sputtering of nanoscale high aspect ratio features. The aspect ratio and sputter yield vary with the ion species and beam energy for a constant beam diameter and are related to the distribution of the nuclear energy loss. Neon ions have a larger sputter yield than the helium ions due to their larger mass and consequently larger nuclear energy loss relative to helium. Quantitative information such as the sputtering yields, the energy-dependent aspect ratios and resolution-limiting effects are discussed.