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Co-diffusion of Er with Ti into LiNbOs produces more than an order of magnitude enhancement in Er diffusivity over that achieved by ion implanting and thermal diffusion. The enhancement is dependent on the amount of Ti present. Er doped channel waveguide fabrication is completely compatible with standard Ti:LiNbOs technology. Fluorescence measurements from co-diffused and bulk grown Er doped LiNbOs show that the co-diffused Er3 + is in the LiNbO, phase.LiNbOs guided wave optics has produced the most sophisticated integrated optic structures to date, but the technology lacks the ability to produce or amplify light. Guided wave lasing and amplification have been reported in channel waveguides fabricated in bulk-grown Nd: LiNbOS.'.2 Bulk-doped materials are, however, not the optimal solution for guided wave integrated optics since absorption will occur in every section of the waveguide which is not optically pumped to transparency. Lateral confinement of the gain medium is also necessary to avoid absorption of the evanescent field. From a telecommunications perspective, Er is a more interesting rare-earth dopant due to its long lived -1.5 ,um radiative transition. Previous attempts to develop techniques which could be used to locally dope LiiOs with Er have met with limited success. Ion implanting ( lOI cm '-' dose of 200 keV Er ions) followed by a thermal annealing at 1050 "C for 45 h produced a l/e depth of 1.8 pm.3 A modest optical gain (0.75 dB) has been recently reported4 from similarly prepared channel waveguides. Guided wave stimulated emission at 1.53 ,um has also been observed5 after extended heating (80 h at 1060 "C) of an Er coated LiNb03 substrate. In this letter we demonstrate that the diffusivity of Er in LiNb03 can be dramatically enhanced by co-diffusing Ti with Er. Fluorescence spectra from co-diffused Er:Ti:LiNb03 and bulk doped Er:LiNbOs are nearly identical.Channel waveguides were photolithographically defined on z-cut LiNb03. Er and Ti/Er thin films were deposited by ion beam sputtering onto a photoresist patterned substrate or directly onto LiNbO, (planar diffusions). Er features could not be produced with this (liftoff) technique due to the poor sticking coefficient of Er on LiNb03. However, the films were easily processed if the Er was over-coated with Ti. Diffusions were carried out at 1050 "C under a flowing oxygen atmosphere containing water vapor. To characterize diffusion profiles, samples were mechanically milled at an angle with a rise-to-run of -1:30 (Fig. 1). Two-dimensional Er concentration depth profiles were made by electron microprobe (EMP) scans of the milled region (inset, Fig. 1). One-dimensional profiles were made by averaging successive scans (Fig. 2). Due to secondary x-ray excitations the EMP results represent the average Er content within the volume of the x-ray plume ( -1 ,um diam). An underestimation of the Er penetration is expected because of the plume effects.One-dimensional depth profiles from four Er diffusion experiments are shown in Fig. 2. In each case the Er f...

X-ray scattering is used to investigate the surface dynamics on Au(111) during Ar+ ion irradiation. During 500 eV Ar+ ion irradiation, we observe the three regimes of step retraction, quasi-layer-by-layer removal and three dimensional rough erosion, analagous to molecular beam epitaxy. The quasi-layer-by-layer sputtering regime has been studied to identify similarities and differences in surface evolution during ion irradiation and molecular beam epitaxy. X-ray measurements suggest that 500 eV Ar+ ion irradiation does not lead to stable adatom island formation. Also, in contrast to molecular beam epitaxy, adatom detachment and diffusion seems important in describing the surface kinetics during ion irradiation.

Using Scanning Tunneling Microscopy(STM) and X-ray diffraction(XRD), we have studied the development of surface roughness on Au(111) during 500eV Ar+ ion irradiation at different angles. During normal incidence erosion the surface roughens and pattern formation occurs. The surface morphology is a mixture of mounds and pits superimposed onto a larger structure of channels and valleys. The characteristic spacing between features grows with a power law behavior t27, where t is the amount of time the sample was irradiated, in agreement with previous measurements[l]. At glancing angles, erosion proceeds smoothly, but not in layer-by-layer fashion. Finally, a combination of glancing angle and normal incidence erosion is used to create a rippled morphology