In this paper, a scheme which can be used in multi-user quantum digital signature is proposed. The scheme of signature and verification is based on the characters of GHZ (Greenber- ger-Horne-Zeilinger) states and controlled quantum teleportation. Different from the digital signatures based on computational com- plexity, this scheme is unconditional secure, and compared to the former presented quantum signature scheme, it does not rely on an arbitrator to verify the signature and realize a message can be signed by multi-user together.
Metallic copper(Cu) films were deposited on a Si (100) substrate by unbalancedmagnetron sputtering enhanced by radio-frequency plasma and external magnetic field confine-ment.The morphology and structure of the films were examined by scanning electron microscopy(SEM),atomic force microscope (AFM) and X-ray diffraction (XRD).The surface average rough-ness of the deposited Cu films was characterized by AFM data and resistivity was measured bya four-point probe.The results show that the Cu films deposited with radio-frequency dischargeenhanced ionization and external magnetic field confinement have a smooth surface,low surfaceroughness and low resistivity.The reasons may be that the radio-frequency discharge and externalmagnetic field enhance the plasma density,which further improves the ion bombardment effectunder the same bias voltage conditions.Ion bombardment can obviously influence the growthfeatures and characteristics of the deposited Cu films.
The ion line of 434.8 nm and atom line of 419.8 nm of Ar plasma produced byan inductively coupled plasma (ICP) were measured by optical emission spectroscopy and theinfluences from the working gas pressure,radio-frequency (RF) power and different positions inthe discharge chamber on the line intensities were investigated in this study.It was found that theintensity of Ar atom line increased firstly and then saturated with the increase of the pressure.Theline intensity of Ar^+,on the other hand,reached a maximum value and then decreased along withthe pressure.The intensity of the line in an RF discharge also demonstrated a jumping mode and ahysteresis phenomenon with the RF power.When the RF power increased to 400 W,the dischargejumped from the E-mode to the H-mode where the line intensity of Ar atom demonstrated a suddenincrease,while the intensity of Ar+ ion only changed slightly.If the RF power decreased from ahigh value,e.g.,1000 W,the discharge would jump from the H-mode back to the E-mode at apower of 300 W.At this time the intensities of Ar and Ar+ lines would also decrease sharply.Itwas also noticed in this paper that the intensity of the ion line depended on the detective locationin the chamber,namely at the bottom of the chamber the line was more intense than that in themiddle of the chamber,but less intense than at the top,which is considered to be related to thecapacitance coupling ability of the ICP plasma in different discharge areas.
