The calcite material analyzed was optical-quality
Iceland spar (purchased from Geocity AB, Stockholm, mined in Madagascar)
cleaved to provide a uniform fresh surface with stainless steel chisel
and hammer,23 (link) following the natural crystal
angles of the rhombohedron along the dominant {101̅4} cleavage
plane. This highly hygroscopic and wettable surface32 (link),33 (link) was immediately purged with pressurized nitrogen (industrial quality:
nitrogen ≥99.9 vol %, oxygen ≤20 ppm, water ≤10
ppm). At least three samples for each study were analyzed, each being
a few millimeters thick with an approximate surface area of 50–100
mm2, and with no evidence of microcracks or excessive surface
steps. Epoxy glue (Bostik, France) was used for sample attachment
to the magnetic disk used in the AFM studies. A sapphire calibration
sample (Bruker) was used for deflection sensitivity calibration of
the AFM probes, and a titanium roughness sample (RS-12M, Bruker) for
the determination of the probes’ tip end radii. Stearic acid
(C18) (Sigma-Aldrich, ≥97.0%) was used for modification
of the calcite surface.
Iceland spar (purchased from Geocity AB, Stockholm, mined in Madagascar)
cleaved to provide a uniform fresh surface with stainless steel chisel
and hammer,23 (link) following the natural crystal
angles of the rhombohedron along the dominant {101̅4} cleavage
plane. This highly hygroscopic and wettable surface32 (link),33 (link) was immediately purged with pressurized nitrogen (industrial quality:
nitrogen ≥99.9 vol %, oxygen ≤20 ppm, water ≤10
ppm). At least three samples for each study were analyzed, each being
a few millimeters thick with an approximate surface area of 50–100
mm2, and with no evidence of microcracks or excessive surface
steps. Epoxy glue (Bostik, France) was used for sample attachment
to the magnetic disk used in the AFM studies. A sapphire calibration
sample (Bruker) was used for deflection sensitivity calibration of
the AFM probes, and a titanium roughness sample (RS-12M, Bruker) for
the determination of the probes’ tip end radii. Stearic acid
(C18) (Sigma-Aldrich, ≥97.0%) was used for modification
of the calcite surface.
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