Solid-State Acquisition of Fingermark Topology using Dense Columnar Thin Films

Abstract

Various vacuum techniques are employed to develop fingermarks on evidentiary items. In this work, a vacuum was used to deposit columnar thin films (CTFs) on untreated, cyanoacrylate-fumed or dusted fingermarks on a limited selection of nonporous surfaces (microscope glass slides and evidence tape). CTF deposition was not attempted on fingermarks deposited on porous surfaces. The fingermarks were placed in a vacuum chamber with the fingermark side facing an evaporating source boat containing either chalcogenide glass or MgF(2). Thermal evaporation of chalcogenide glass or MgF(2) under a 1 μTorr vacuum for 30 min formed dense CTFs on fingermark ridges, capturing the topographical features. The results show that it is possible to capture fingermark topology using CTFs on selected untreated, vacuumed cyanoacrylate-fumed or black powder-dusted nonporous surfaces. Additionally, the results suggested this might be a mechanism to help elucidate the sequence of deposition.

Optimized Development of Sebaceous Fingermarks on Nonporous Substrates with Conformal Columnar Thin Films

“…Whereas the base pressure was 4.0 × 10 −6 Torr or lower in the predecessor studies , it was determined that just 1.0 × 10 −4 Torr would suffice for fingermark development. The adequate base pressure thus determined is moderately low, which greatly reduces the requirements on CEFR apparatus for fingermark development, specifically the time needed to pump down to the base pressure.…”

Quality of development of latent sebaceous fingerprints coated with thin films of different morphologies

“…None of the aforementioned development techniques for visualizing latent fingerprints takes advantage of the ridgeand-valley topology of the fingerprint residue, but a new visualization technique 12,13 does exactly that by conformally coating the top of the latent fingerprint by a columnar thin film (CTF). 14,15 A CTF is an assembly of parallel nanocolumns typically grown by physical-vapor-deposition techniques such as thermal evaporation, electron-beam evaporation, sputtering, and ion-beam-assisted evaporation.…”

Vacuum-metal-deposition and columnar-thin-film techniques implemented in the same apparatus

“…If the platform is stationary, tilted nanocolumns form on the surface of the fingerprint residue. If the platform is rapidly rotated about an axis which passes normally through it, upright and parallel nanocolumns form [8,10] and the development quality is significantly better [11]. The bottom panel in Fig.…”

“…A currently emerging technique for physical-vapor-deposition technique which conformally coats the surface of the latent fingerprint with upright or tilted nanocolumns with a columnar thin film (CTF) does exactly that [8,9]. In the CTF technique, the source material kept in a receptacle inside a low-pressure chamber is resistively heated until a collimated vapor is generated.…”