Figure 2. (a) Current versus voltage evolution computed for the energetically most stable n-Si(100)|aTiSi models using a Si n-type doping concentration of 10 20 |e|/cm 3. The dash-dotted line shows the linear regime used in the extraction of the contact resistance. (b) Corresponding evolution of the position dependent (X axis) Local Density Of States (LDOS) (Y axis) computed at a bias of 0 Volt for the energetically most stable n-Si(100)|aTiSi models. The X axis reflects the position along the main axis of the n-Si(100)|aTiSi interface (Figure 1). The zero of the energy is set to the Fermi level (E F ). High and low density of states are colored in a hue spanning from pink to black respectively. The averaged Hartree potential is added as a guide line for the eyes and aligned on the top of the valence and bottom of the conduction band as continuous white lines. Vertical dashed lines point the position of the interface and the presence of MIGS states. 

The disordered nature of amorphous metals such as TiSi makes the simulation of their interfaces with silicon complex. Indeed, the degrees of freedom at the interface in terms of local bond lengths, coordination number and composition make the development of an interface model challenging. In an attempt to capture these effects, we investigated the contact resistance of four different Si(100)-aTiSi interface models, in which the Ti and Si concentrations set in contact with the silicon substrate, their local coordination and bond lengths were varied. An atomistic model corresponding to the most stable energetic configuration is illustrated in Figure 1. All models lead to a current versus voltage (I.V.) characteristic curves similar to the one reported in Figure 2a, where a linear evolution of the current versus the applied voltage is obtained up to a bias of ∼0.1 V, after which the systems display a non-ideal linear behavior. The linear regime evolution was then used to extract the intrinsic contact resistance of the modeled interface. For instance, the intrinsic contact resistance of Figure 1 corresponds to 9.5 × 10 −8 .cm 2 for a doping concentration of 1 × 10 20 |e|/cm 3 and reflects the needs for the injected electrons to cross the interface potential set by the tail states 19 present at the metal-semiconductor interface (Figure 2b). Interestingly, this model leads to contact resistances values relatively close to what has been recently measured experimentally by Hao et al., 15 as illustrated in Figure 3a. As expected, the contact resistance evolves linearly with the doping concentration to reach values as low as 1.8 × 10 −10 .cm 2 for an active doping concentration of 1 × 10 22 |e|/cm 3 . These findings are consistent with the recent demonstration of a sub 10 −9 .cm 2 con- tact resistance for PMOS devices. 20 Remarkably, the first-principles simulations also suggest that beyond this value the contact resistance should saturate, even for a completely unrealistic active dopant con- centration of 1 × 10 23 |e|/cm 3 .

The disordered nature of amorphous metals such as TiSi makes the simulation of their interfaces with silicon complex. Indeed, the degrees of freedom at the interface in terms of local bond lengths, coordination number and composition make the development of an interface model challenging. In an attempt to capture these effects, we investigated the contact resistance of four different Si(100)-aTiSi interface models, in which the Ti and Si concentrations set in contact with the silicon substrate, their local coordination and bond lengths were varied. An atomistic model corresponding to the most stable energetic configuration is illustrated in Figure 1. All models lead to a current versus voltage (I.V.) characteristic curves similar to the one reported in Figure 2a, where a linear evolution of the current versus the applied voltage is obtained up to a bias of ∼0.1 V, after which the systems display a non-ideal linear behavior. The linear regime evolution was then used to extract the intrinsic contact resistance of the modeled interface. For instance, the intrinsic contact resistance of Figure 1 corresponds to 9.5 × 10 −8 .cm 2 for a doping concentration of 1 × 10 20 |e|/cm 3 and reflects the needs for the injected electrons to cross the interface potential set by the tail states 19 present at the metal-semiconductor interface (Figure 2b). Interestingly, this model leads to contact resistances values relatively close to what has been recently measured experimentally by Hao et al., 15 as illustrated in Figure 3a. As expected, the contact resistance evolves linearly with the doping concentration to reach values as low as 1.8 × 10 −10 .cm 2 for an active doping concentration of 1 × 10 22 |e|/cm 3 . These findings are consistent with the recent demonstration of a sub 10 −9 .cm 2 con- tact resistance for PMOS devices. 20 Remarkably, the first-principles simulations also suggest that beyond this value the contact resistance should saturate, even for a completely unrealistic active dopant con- centration of 1 × 10 23 |e|/cm 3 .