## 3 Results
### Electrical Conductivity of Laser Sintered NP Arrays  
Laser sintering of silver NP arrays in the form of lines was done by each of the four lasers with a large number of regimes. They were characterized by a change of supplied specific energy per surface unit in the range from five to six magnitude orders. At a given laser radiation average power, the specific energy supplied to the surface of the array was controlled by changing the speed of the laser beam relative to the line. In all the experiments, the diameter of the laser beam exceeded the width of the line. It provided the radiation energy supply to the entire surface of the sample during the  
Figure 3: Characterization of primary nanoparticles: (**a**) TEM image of agglomerates consisting of primary NP; (**b**) A size distribution of the agglomerates measured in the aerosol flow by NP analyzer MIPS 3936; (**c**) The SEM image of the non-sintered NP array surface.  
movement of the beam. Figure 4a-d shows the experimental dependencies of the average specific conductivity \(\sigma\) of sintered silver NP arrays at several fixed values of the average laser power versus the specific energy e in logarithmic coordinates. Here, each experimental point on the graphs \(\sigma\)(**e**) corresponds to the average value of the conductivity measurements of at least three samples.  
The \(\sigma\)(e) behavior tends to increase in conductivity maximum value with an increase of radiation power for all laser radiation types. There are exceptions to this behavior shown in Figure 4a-c, where for the maximum laser powers the dependences \(\sigma\)(e) are lower than for the preceding powers. This may indicate the existence of some optimal radiation power resulting in maximum conductivity for a particular type of radiation. Most of the obtained dependences \(\sigma\)(e) are characterized by monotonically increasing curves. However, only for pulsed lasers (Figure 4a,b) the dependences of the average conductivity on the specific energy have a pronounced maximum. It is worth mentioning that with the energy density increase for radiation with a wavelength 1054 nm (Figure 4b) the decay in conductivity tends to go smoothly, while for radiation with a wavelength 527 nm (Figure 4a) the conductivity decreases steeply, reaching lower values as compared to the minimum power. It can be assumed that there is an optimum for the energy density supplied to the sample in pulse mode, in which higher energy values lead to degrading or destruction of the sample. In terms of the absolute value of specific  
Figure 4: The dependence of the specific electrical conductivity \(\sigma\) of sintered NP arrays versus the specific energy supplied to the sample e for pulsed laser radiation with wavelengths (**a**) 527 nm, (**b**) 1054 nm and continuous laser radiation with wavelengths (**c**) 527 nm, (**d**) 980 nm at different values of their average power.  
conductivity, the highest values were achieved for sintered samples using CW laser radiation with a wavelength 980 nm. The specific conductivity achieved in this regime corresponds to the half of the bulk silver conductivity (Figure 4d).  
It should be noted that CW laser sintering showed a higher specific conductivity in comparison with the pulsed laser sintering. The sintering of samples under the laser radiation with a wavelength 527 nm required significantly lower specific energy costs as compared to the longwave laser sintering. Similarly, it is more efficient to conduct sintering with pulsed laser radiation than with CW.