E. P. Münger

Energy distributions of positive and negative ions during magnetron sputtering of an Al target in Ar∕O2 mixtures

The ion flux obtained during reactive magnetron sputtering of an Al target in Ar/O2 gas mixtures was studied by energy-resolved mass spectrometry, as a function of the total and O2 partial pressure ...

Low‐temperature deposition of cubic BN:C films by unbalanced direct current magnetron sputtering of a B4C target

Controllable‐unbalanced dc magnetron sputtering of a B4C target in mixed Ar–N2 discharges has been used to deposit BN:C thin films with carbon concentrations in the range of 5–21 at. % on Si(001) substrates. The variation of the nitrogen gas consumption with nitrogen partial pressure was used to determine the sorption capacity of the sputtering source and was then correlated to the film elemental composition. An additional axially symmetric magnetic field was used to vary the discharge plasma density near the substrate in a wide range. Hence, the ion flux Ji of primary Ar+ and N+2 ions accelerated to the substrate by an applied negative substrate bias could be varied while keeping the deposition flux Jn (the sum of film building species, B, C, and N atoms) near constant. BN:C films were grown at large ion‐to‐neutral flux ratios 3≤Ji/Jn≤24, ion energies Ei≤500 eV, and substrate temperatures 150≤Ts≤350 °C. The phase and elemental composition of as‐deposited BN:C films were characterized by Fourier transform...

Reptation: a mechanism for cluster migration on (111) face-centered-cubic metal surfaces

Abstract Embedded-atom molecular-dynamics simulations were used to follow the diffusion dynamics of compact platinum clusters with up to 19 atoms on Pt(111). The results reveal a cluster diffusion mechanism on (111) face-centered-cubic (fcc) surfaces involving successive shear translations of adjacent subcluster regions giving rise to reptation, a snake-like gliding motion. We show that for compact clusters with

Asymmetric interface broadening in epitaxial Mo/W (001) superlattices grown by magnetron sputtering

The interfacial structure in epitaxial Mo/W(001) superlattices, grown by magnetron sputtering on MgO(001) substrates has been studied. The films were grown in Ar and Kr discharges at a substrate temperature of 700 °C, and the as-deposited samples were analyzed by x-ray diffraction and found to be epitaxial with no high-angle grain boundaries. The degree of interfacial intermixing, caused by fluxes of different energetic species impinging on the growth surface, was estimated using a combination of Monte Carlo binary collision computer codes and a gas scattering computational model. In the Ar discharge case, large asymmetries in the Mo/W and W/Mo interfaces were found, with the W/Mo interface being more than a factor of 2 broader than the Mo/W interface. Simulations of x-ray reflectivity curves using the calculated interface profiles as input parameters without any additional fitting parameters agreed very well with measured data. The overall good fit between the calculated and measured reflectivity curves ...

Low-energy ion irradiation during film growth: Kinetic pathways leading to enhanced adatom migration rates

Embedded-atom molecular dynamics simulations are used to investigate the effects of low-energy self-ion irradiation of Pt adatoms on Pt(111). Here, we concentrate on self-bombardment dynamics, i.e. ...

Enhanced cluster mobilities on Pt(111) during film growth from the vapor phase

We use molecular dynamics simulations to follow the dynamics of small two-dimensional Pt clusters on Pt(111) at 1000 K. While close-packed Pt7 heptamers are extremely stable structures, the addition of a single cluster vacancy or an on-top adatom immediately results in intracluster bond breaking, reconfigurations, rotations, the introduction of stacking faults, and greatly enhanced cluster diffusion rates. Mapping center-of-mass motion for total simulation times >145 ns revealed increases in cluster velocities by more than an order of magnitude with cluster migration occurring primarily by concerted motion and a novel diffusion mechanism involving double shearing of dimers/trimers. Contrary to some previous reports, edge-atom diffusion plays only a minor role.

Adatom-induced diffusion of two-dimensional close-packed Pt7 clusters on Pt(111)

Abstract Molecular dynamics simulations were used to follow the dynamics of the motion of hexagonal Pt heptamers on Pt(111). Closepacked Pt 7 clusters on fcc sites were found to be very stable structures with reconfiguration or translation events occurring only rarely over simulation times > 30 ns at 1000 K. The adsorption of a single adatom on the cluster surface, however, induced rapid intracluster bond breaking, reconfiguration, the introduction of stacking faults, and greatly enhanced cluster diffusion rates. Cluster migration occurred primarily through sequences of individual atom and concerted dimer jumps, but concerted cluster motion was also observed. The adatoms eventually descended to the terrace, predominantly through push-out/exchange reactions with cluster atoms at B edges.

Unravelling the physical mechanisms that determine microstructural evolution of ultrathin Volmer-Weber films

The initial formation stages (i.e., island nucleation, island growth, and island coalescence) set characteristic length scales during growth of thin films from the vapour phase. They are, thus, dec ...

Dynamic competition between island growth and coalescence in metal-on-insulator deposition

The morphology of thin metal films and nanostructures synthesized from the vapor phase on insulating substrates is strongly influenced by the coalescence of islands. Here, we derive analytically the quantitative criterion for coalescence suppression by combining atomistic nucleation theory and a classical model of coalescence. Growth simulations show that using this criterion, a coalescence-free growth regime can be reached in which morphological evolution is solely determined by island nucleation, growth, and impingement. Experimental validation for the ability to control the rate of coalescence using this criterion and navigate between different growth regimes is provided by in situ monitoring of Ag deposition on SiO2. Our findings pave the way for creating thin films and nanostructures that exhibit a wide range of morphologies and physical attributes in a knowledge-based manner.

Low-temperature alpha-alumina thin film growth : ab initio studies of Al adatom surface migration

Investigations of activation energy barriers for Al surface hopping on alpha-Al2O3 (0 0 0 1) surfaces have been carried out by means of first-principles density functional theory calculations and t ...