TRACKING THERMALLY DRIVEN MOLECULAR REACTION AND FRAGMENTATION BY FAST PHOTOEMISSION: C₆₀on Si(111)

Abstract

We followed in real time the thermal reaction of fullerene molecules with the Si(111) surface by means of fast photoemission spectroscopy. The formation of SiC via C60 fragmentation on Si(111) is used as a key example of the capability of fast photoemission, associated with a fine temperature control, in determining the nature of thermally induced chemical reactions. By monitoring every 13 s the evolution of the C1s core level photoemission spectrum, as a function of temperature and as a function of time at fixed temperature, we were able to identify several steps in the interaction of C60 with Si(111). A model describing the thermal evolution of this interaction, in agreement with these and other experimental observations, considers the initial chemisorption of C60 in mainly metastable configurations, the evolution toward more stable configurations, allowed by molecular rotations and breaking of Si-Si bonds, the cage deformation to further increase the number of C-Si bonds, the final cage fragmentation and SiC formation only above 1050 ± 10 K.

Substrate Influence for the Zn‐tetraphenyl‐porphyrin Adsorption Geometry and the Interface‐Induced Electron Transfer

“…However, we note the presence of a small feature at lower binding energy, which is related to the CÀSi bonds. [33] The area of the CÀSi peak corresponds to about 2 atoms compared to the total area.…”

Tuning 3C-SiC(100)/Si(100) Heterostructure Interface Quality

“…As a consequence, the growth temperature must be chosen as low as possible, but at the same time, it must be high enough to allow the formation of 3C-SiC layers with high crystallographic properties. Three different growth temperatures were selected, 1050 K (minimum temperature to form SiC , ), 1200, and 1370 K, corresponding to three significantly different growth conditions. At 1050 K, the reaction time (time necessary for the complete reaction of C 60 molecules with the Si substrate to form covalent Si-C bonds obtaining SiC, as shown in ref and references therein) is rather slow, about 300 s, and the possibility to grow well-ordered samples might be reached only by fixing the C 60 flux to a low rate, as discussed below.…”

“…Among the many growth methods and precursors exploited so far, the C 60 molecules have been successfully used as a carbon source to synthesize 3C-SiC films on Si substrates even if the interface shows several defects. − As we demonstrate in the following, the appropriate choice of codeposited Si and C 60 fluxes and growth temperature allows the reduction of the Si atom effusion from the substrate, which is mainly responsible for the large number of defect and void formation at the interface. Moreover, by using Si and C 60 , no extra chemical species are present in the precursors, limiting the chemical contamination of the grown SiC layer (H-free).…”

“…Indeed, the morphology of the thin films reflects the morphology of the substrate, such as the number of defects of the grown film is related to the number of defects of the substrate surface itself . Generally, samples obtained by codeposition (showing pits of pyramidal shape at the SiC/Si interface and holes on the surface ,− ,− ) are grown by using high growth flux rate and poor base pressure (≈1 × 10 –7 –1 × 10 –8 mbar) conditions in which it is extremely hard to obtain well-ordered, flat, and defect-free clean Si substrates. , …”

SiC formation by C60 molecules as a precursor: A synchrotron-radiation photoemission study of the carbonization process

“…Reaction of C 60 with the Si substrate yields a SiC film, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] which avoids extraneous species and improves the structural quality of the interface between SiC and Si. The temperature of the silicon substrate is kept near 800°C, notably less than for CVD.…”