Effect of roughness and nanoporosity on optical properties of black and reflective Al films prepared by magnetron sputtering

Thermal Stability of Black Aluminum Films and Growth of Aluminum Nanowires from Mechanical Defects on the Film Surface during Annealing

“…The bottom surface of the films is always a nonporous layer, which explains its reflective properties. [ 14 ] The top surface of the films, however, has a sponge‐like porous structure with grains as evidenced by SEM ( Figure 2 ). Also, the surface of the films was relatively soft and could easily develop mechanical defects, such as small abrasions and scratches, during transportation and further handling of the samples.…”

“…Black Al film is rich in defects due to the presence of impurities used to get the low reflective structure with columnar nanopores, as reported in our previous works. [14,39] During the nanowire growth, Al atoms, as well as nitrogen and oxygen atoms, will be extruded and produce twins, which will change the orientation of nanowire growth and generate the spiral shape. This effect was not reported in previous works [34][35][36][37] because Al films deposited in these works had a reflective surface.…”

“…Generally, black metals are considered to be stable up to 300 °C. [ 5 ] Several metals, such as silver, [ 6 ] gold, [ 7,8 ] platinum, [ 9 ] tungsten, [ 10 ] titanium, [ 11 ] palladium, [ 12 ] and aluminum, [ 13,14 ] are known to be fabricated in the form of black metals. Black aluminum (Black Al) is a metal that has good thermal stability and at the same time is inexpensive to produce.…”

“…[3,4] Such coatings must have good thermal stability, namely they must retain their porous structure and, consequently, heatabsorbing properties at elevated temperatures. Generally, black metals are considered to be stable up to 300 C. [5] Several metals, such as silver, [6] gold, [7,8] platinum, [9] tungsten, [10] titanium, [11] palladium, [12] and aluminum, [13,14] are known to be fabricated in the form of black metals. Black aluminum (Black Al) is a metal that has good thermal stability and at the same time is inexpensive to produce.…”

Surface Enhancement Using Black Coatings for Sensor Applications

“…Black metals (BMs) are defined as highly porous nanocrystalline materials that can significantly trap incident light [ 11 , 12 , 13 ]. These porosities are introduced during the growth of the metal film due to the presence of impurities which creates a structure allowing complex subwavelength electromagnetic interactions with the light in wide wavebands [ 14 ].…”