Facet‐Dependent Electrical Conductivity Properties of Silver Oxide Crystals

Abstract

Ag O cubes, truncated octahedra, rhombic dodecahedra, and rhombicuboctahedra were synthesized in aqueous solution. Two tungsten probes were brought into contact with a single particle for electrical conductivity measurements. Strongly facet-dependent electrical conductivity behaviors have been observed. The {111} faces are most conductive. The {100} faces are moderately conductive. The {110} faces are nearly non-conductive. When electrodes contacted two different facets of a rhombicuboctahedron, asymmetrical I-V curves were obtained. The {111} and {110} combination gives the best I-V curve expected for a p-n junction with current flowing in one direction through the crystal but not in the opposite direction. Density of states (DOS) plots for varying number of different lattice planes of Ag O match with the experimental results, suggesting that the {111} faces are most electrically conductive. The thicknesses of the thin surface layer responsible for the facet-dependent properties of Ag O crystals have been determined.

Density Functional Theory Calculations Revealing Metal‐like Band Structures for Ultrathin Germanium (111) and (211) Surface Layers

“…[7,8] Densityf unctional theory (DFT) calculations performed on Cu 2 O, Ag 2 O, and PbS have revealed distinctly different band structures and density-of-states( DOS) plots within af ew (100), (110), and( 111) surfacep lanes, which can be very insightful to understandingt he observed electrical-conductivity differences. [2,3,6] The DFT calculations conducted on at unable number of ap articularl attice plane support the idea of the existence of an ultrathin surface layer with different degrees of valence and conduction band bending for these crystal faces. This model is also very useful to explain widely observed facet-dependent photocatalytic properties of many semiconductor materials and heterostructures, in which photocatalytic activities can vary from highly active to completely suppressed depending on the exposed or contacting facets as seen in Cu 2 Oc rystals and Cu 2 O-ZnOh eterostructures.…”

“…Various semiconductor materials includingC u 2 O, [1,2] Ag 2 O, [3] TiO 2 , [4,5] and PbS [6] crystals have been shown to exhibit strongly facet-dependent electrical conductivity behavior.F or example, the same Cu 2 Op articlec an simultaneously behavel ike a metal, as emiconductor,a nd an insulator depending on the measured crystal facets, therebyc hanging our understanding of semiconductor behavior.D espite the poor electrical-conductivity responses due to the large energy band gaps of Ag 3 PO 4 , Ag 3 PO 4 crystals still shows light face-specifice lectrical-conductivity differences. [7,8] Densityf unctional theory (DFT) calculations performed on Cu 2 O, Ag 2 O, and PbS have revealed distinctly different band structures and density-of-states( DOS) plots within af ew (100), (110), and( 111) surfacep lanes, which can be very insightful to understandingt he observed electrical-conductivity differences.…”

Density Functional Theory Calculations Revealing Metal‐like Band Structures and Work Function Variation for Ultrathin Gallium Arsenide (111) Surface Layers

“…Cu 2 O, Ag 2 O, TiO 2 ,a nd PbS crystalsh aveb een shown to exhibit strongly facet-dependent electricalc onductivity behaviors. [1][2][3][4][5] For example, aC u 2 Oo ctahedron is highlyc onductive, but a single Cu 2 Or hombic dodecahedron is insulating. More recently,i ntrinsic Si and Ge wafers have also revealed facet-dependent electronic properties.…”

Silicon Wafers with Facet‐Dependent Electrical Conductivity Properties

“…[1][2][3][4][5][6] These interesting semiconductor properties can be explained in terms of the presence of an ultrathin surface layer having varying degrees of band bending for different surface planes.T his effect controls the relative obstacle of charge transport through asemiconductor crystal depending on the points of electrical contacts.S uch af eature is highly useful for electronic component design. [1][2][3][4][5][6] These interesting semiconductor properties can be explained in terms of the presence of an ultrathin surface layer having varying degrees of band bending for different surface planes.T his effect controls the relative obstacle of charge transport through asemiconductor crystal depending on the points of electrical contacts.S uch af eature is highly useful for electronic component design.…”

“…Again the two probes are close to each other within afew micrometers to reduce the current path length. [1,[4][5][6] Remarkably,a ll facet combinations exhibit asymmetrical behaviors.P ossibly because both Si {100} and {110} facets are barely conductive in the low-voltage region, connecting these poorly conducting facets still gives roughly symmetrical I-V curves with intermediate current magnitude.A nother way to reveal additional insights from these I-V curves is to present their electrical resistance diagrams.T he {100}/{110} case shows very large electrical resistance for both current directions in the + 2V to À2V range than the other facet combinations (Figure 4a Figure S6). Themain purpose of such measurements is to see if asymmetrical I-V curves can be obtained as seen previously for Cu 2 O, Ag 2 O, TiO 2 ,a nd PbS micro-and sub-microcrystals.…”