Surface morphology changes during Pb deposition on Cu(100): evidence for surface alloyed Cu(100)–c(2×2) Pb

Abstract

e describe the rnicrofabrication of a multi-level diffractive optical element (DOE) onto a micro-electromechanical system (MEMS) as a key element in an integrated compact optical-MEMS laser scanner. The DOE is a four-level off-axis microlens fabricated onto a movable polysilicon shuttle. The microlens is patterned by electron beam lithography and etched by reactive ion beam etching. The DOE was fabricated on two generations of MEMS components. The first generation design uses a shuttle suspended on springs and displaced by a linear rack. The second generation design uses a shuttle guided by roller bearings and driven by a single reciprocating gear. Both the linear rack and the reciprocating gear are driven by a microengine assembly. The compact design is based on mounting the MEMS module and a vertical cavity surface emitting laser (VCSEL) onto a fused silica substrate that contains the rest of the optical system. The estimated scan range of the system is &4°with a spot size of 0.5 mm. INTRODUCTIONMicro-electromechanical systems (MEMS) is a primarily silicon-based technology that brings precision motion to the microscopic scale using batch fabrication processes developed as extensions from the silicon integrated circuit industry. Compared to the macroscopic systems whose functions they emulate, MEMS are smaller, lighter, lower cost, and more efficient (lower power consumption). For many applications, it is desirable to incorporate optical functions with MEMS. This requires a hybrid approach to integrate compound semiconductor-based light emitters and some form of rnicrooptics, e.g., diffractive optical elements (DOES), to create an integrated microsystem.Integrated Microsystems is an emerging technology in which electrical, optical, and mechanical functions are combined at the chip level into compact, lightweight, and [ultimately] low cost modules with performance equal to or even exceeding those of conventional macroscopic systems. The development of integrated rnicrosystems is expected to revolutionize abroad range of fields, extending beyond electro/optomechanical systems to the fields of biology, chemistry and medicine. Just as the integrated circuit combines formerly discrete devices (transistors, resistors, capacitors) onto a single chip with increasing functionality at DISCLAIMERPortions of this document may be illegible in electronic image products.Images are produced from the best available original document. AbstractUsing Low Energy Electron Microscopy (LEEM), we have followed Cu(l 00) surface morphology changes during Pb deposition at different temperatures. Surface steps advance and 2-D islands nucleate and grow as deposited Pb first alloys, and then dealloys, on a 125°C CU(1OO) surface. From LEEM images, we determine how much Cu is being displaced at each stage and find that the amount of material added to the top layer for a complete Pb/Cu(100) c(4x4) reconstruction (a surface alloy) is consistent with the expected c(4x4) Cu content of 0.5 monolayer. However, as the surface changes to the Pb/Cu...

Relationship between domain-boundary free energy and the temperature dependence of stress-domain patterns of Pb on Cu(111)

“…21 Details on experimental preparation and the setup have been published elsewhere. 22,23 Boundary energy measurements were performed at half area fraction, i.e., the amount of Pb that was deposited was such that the surface alloy and overlayer phase covered half the visible surface area, as in Fig. 2.…”

Surface phase transition and electronic structure of c(5√2×√2)R45°-Pb/Cu(100)

“…The growth of submonolayer amounts of Pb on Cu(1 0 0) has deserved ample attention in the past [9][10][11][12][13][14][15][16][17][18][19][20]. In the following, we summarize briefly the most relevant properties of this system.…”

“…For a more detailed account we refer the reader to Refs. [19,20]. On the one hand, Pb and Cu are immiscible in the bulk, but Pb atoms intermix with Cu in the earliest stages of the growth [16].…”

“…The total energy (angular) resolution in beamline 33 was 50 meV (0.50°), 30 meV (0.12°) in MaxLab and 50 meV (0.50°) in our home laboratory. The c(5 p 2 · p 2)R45°structure is observed after deposition of 0.6 ML of Pb at 300 K followed by a slight anneal at 400 K. The coverage is calibrated from the sequence of structures below 0.6 ML [9][10][11][12][13][14][15][16][17][18][19][20] and from the Pb 5d/Cu 3d intensity ratio. Symmetry points are referred to the Cu(1 0 0) surface Brillouin zone, unless otherwise stated.…”

Factors Affecting the Coverage Dependence of the Diffusivity of One Metal over the Surface of Another

“…7a. This phase diagram has been inferred [8] from several recent literature reports of the surface phases present as a function of coverage [14][15][16]. Although the measurements underlying Fig.…”