Surface chemical reactions induced by well-controlled molecular beams: translational energy and molecular orientation control

Abstract

I review our recent studies of chemical reactions on single-crystalline Cu and Si surfaces induced by hyperthermal oxygen molecular beams and by oriented molecular beams, respectively. Studies of oxide formation on Cu induced by hyperthermal molecular beams suggest that the translational energy of the incident molecules plays a significant role. The use of hyperthermal molecular beams enables us to open up new chemical reaction paths, and to develop new methods for the fabrication of thin films. Oriented molecular beams also demonstrate the possibility for controlling surface chemical reactions by varying the orientation of the incident molecules. The steric effects found on Si surfaces hint at new ways of achieving material fabrication on Si surfaces. Controlling the initial conditions of incoming molecules is a powerful tool for creating new materials on surfaces with well-controlled chemical reactions.

Supersonic Molecular Beam Experiments on Surface Chemical Reactions

“…Cross-sectional top view of the main parts of the surface chemistry experimental station SUREAC2000 installed at BL23SU at the SPring-8 facilities. [57,91] Chem. Rec.…”

“…Steric effects of reactants have been reported in the collision dynamics and reactions for several systems. [73,81,91] In particular, the role of the incoming molecular orientation in the precursor-mediated adsorption on Si has been understood, suggesting the general importance of steric effects in the chemical reactions of organic molecules with Si. [90][91][92][93][94] Figure 11a shows the surfacetemperature dependence of initial sticking probability SRandom for the random-orientation CH3Cl of |JKM〉= |111〉 (full red circles) and |212〉 (open blue circles) states at Ei = 120 meV.…”

“…Thus, we perform the direct observation of the surface products created by the oriented NO beam. [91,102,103] Figure 14 shows the orientation dependence of the O-1s and N-1s XPS spectra, measured at ΘTotal ≈ 0.28 ML for the 58 meV oriented NO |0.5 0.5 0.5〉 beam at Ts = 400 K. It is clear that an N-end collision is more reactive than an O-end collision. Figure 15 shows the total coverage ΘTotal dependence of the stereo-asymmetric factor R. Here, we define R as follows where Si(t), with i = N or O, is the reactive sticking probability for the N-or O-end collision, respectively.…”

Tunneling Effect of O₂ in Dissociative Adsorption on Pt(111) Surface

“…In the modern molecular beam experiment, the rotational state of the O 2 can be arbitrary selected [22,23]. Thus, the sticking probability of specific molecular orientation can be calibrated.…”

Note: A versatile mass spectrometer chamber for molecular beam and temperature programmed desorption experiments

“…Both techniques have played a leading role in determining adsorption dynamics; 1-3 surface structure and physics; 4-6 and reaction kinetics. [7][8][9] However, the experimental geometry demanded by MBS and TPD are entirely different. To provide increased time and angular resolution, MBS experiments are performed with the mass spectrometer positioned typically 10s of cm from the sample, with a narrow entrance aperture.…”