3 Position (nm) Position (µm) # of molecules 0 200 400 600 800 1000 1200 0 20 40 60 80 0 0.5 1.0 1.5 a) b) 2nm 5nm FIG. 3: a) The processed STM image (see text) reveals both the particle-nature and the quantum wave-nature of the sur- face deposited fullerene molecules in one and the same image. b) A vertical sum over (a) yields the interference curve. The fringe visibility amounts to 36%. The error bars represent the √$_{N}$$_{-noise related to the small number}$$_{N}$ of particles per bin. FIG. 2: STM image of a reconstructed Si (111) 7 × 7 sur- face, covered with immobilized individual fullerenes. Area of this image: 33 × 36 nm $^{2}$; tunneling current I=0.2 nA; sam- ple bias voltage U=+2V; temperature T=30 K. A close up on two fullerenes (see inset) gives a glimpse on the internal ring structure of C 60 (see also [28]). the expected period and orientation. digit one, whereas all other pixels are set to zero. The result of this procedure is shown in Figure 3a, where the bright dots represent the molecules. For a better visu- alization, the pixels were later binned in 5 × 5 boxes. The resulting image reveals five interference fringes in the chosen section. The observed fringe contrast exceeds the classical moir´ e expectation in the presence of van der Waals forces by more than a factor of thirty, and the experiment is offset from the classical result by ten standard devia- tions. Quantum delocalization and interference are there- fore needed for creating high contrast molecular nanopat- terns using non-contact mask imaging. Surface adsorp- tion and imaging is also an intuitive tool in experiments on the foundations of physics, as it allows to visualize the localized but random particle positions within a de- terministic fringe pattern that is prescribed by the free evolution of the delocalized matter wave (Figure 3). The surface probe technique is capable of detecting individual molecules and it is well-suited for future experiments with velocity selected, monodisperse beams of much larger ob- jects in different interferometer configurations [26]. In order to quantify the fringe contrast we perform a vertical sum (along the y-direction) over all rows and arrive at the one-dimensional interference curve. Since the statistical fluctuations are still rather high, with only 1166 molecules per µ m $^{2}$, we sum over twenty horizontal points (along the x-direction) to obtain Figure 3b. The data are well represented by a numerical fit of the form F ( x ) = A sin(2 πx/d + φ$_{0}$ ) + B , from which we extract a fringe visibility of V = A/B = 36 ± 3 %. The statisti- cal error is computed from a Levenberg-Marquardt algo- rithm which is weighted with the Poissonian uncertainty of each individual column in the picture. A similar inter- ference contrast was found in the gravitational velocity selection scheme. This value is lower than the theoreti- cal expectation, but already a linear drift of 2.5 nm per minute of either one grating or the surface is sufficient to explain this observation. In future experiments, thermal drifts can be further reduced by replacing the interfer- ometer support structure by materials of lower thermal expansion. Single molecules may be regarded as functional ele- ments. They may serve as immobilized single-photon emitters [29], organic switches [30], nanomachines [31, 32], transistor components [33] or as nucleation cores for the catalysis of molecular growth. Positioning them on surfaces might thus be crucial in future applications in nanotechnology. Our molecule lithography scheme works at a de Broglie wavelength comparable to that prevail- ing in high-energy electron beam writing. The kinetic energy E$_{kin}$=0.1 eV and the velocity v = 100 m/s can, however, be many orders of magnitude smaller than that of the electrons. It therefore combines the potential of high resolution with minimal damage to the surface. The recorded lattice has a period of 267(3) nm which differs slightly from the expected 257 nm. The 4 % period mismatch is consistent with a linear thermal drift rate, now in the STM instead of the interferometer, as small as 0.4 nm per minute. The experiment was repeated several times, yielding an interference pattern equally close to