CANDIDATES FOR P-DOPING AND N-DOPING OF TRANSITION METAL DICHALCOGENIDE

Abstract

A doped transition metal dichalcogenide (TMD) by (A) using substitution doping within the fractional limit 0x, y0.1 and/or (B) adding elements to pristine TMD within the fractional limit 0z0.1, wherein the TMD is represented by the formula AB.sub.2 where A={Mo, W}, B={S, Se}, and wherein the doped TMD is selected from substitution n-doping: A.sub.(1-x)M.sub.xB.sub.(2-y)X.sub.y; M={Re, Os}, X={F, Cl, Br, I, OH}; substitution p-doping: A.sub.(1-x)M.sub.xB.sub.(2-y)X.sub.y; M={V, Nb, Ta, Ti, Zr, Hf}, X={N, P, As, Sb}; additional atom n-doping: AB.sub.2Z.sub.z; Z={H, Li, Na, K}; additional atom p-doping: AB.sub.2Z.sub.z; Z={N, P, As, F, Cl, Br, I}; or a combination thereof.

Claims

1. A doped transition metal dichalcogenide (TMD) obtained by (A) using substitution doping within the fractional limit 0x, y0.1 and/or (B) adding elements to pristine TMD within the fractional limit 0z0.1, wherein the TMD is represented by the formula AB.sub.2 where A={Mo, W}, B={S, Se}, and wherein the doped TMD is: substitution n-doping: A.sub.(1-x)M.sub.xB.sub.(2-y)X.sub.y; M={Re, Os}, X={F, Cl, Br, I, OH}; substitution p-doping: A.sub.(1-x)M.sub.xB.sub.(2-y)X.sub.y; M={V, Nb, Ta, Ti, Zr, Hf}, X={N, P, As, Sb}; additional atom n-doping: AB.sub.2Z.sub.z; Z={H, Li, Na, K}; additional atom p-doping: AB.sub.2Z.sub.z; Z={N, P, As, F, Cl, Br, I}; or a combination thereof.

2. The doped TMD of claim 1, wherein the doped TMD is a n-doped TMD and has the following formula: $A_{\left(1-x\right)}{M}_x{B}_{\left(2-y\right)}{X}_y;M=\left\{\mathrm{Re},\mathrm{Os}\right\},X=(F,\mathrm{Cl},\mathrm{Br},I,\mathrm{OH}\},A=\left\{\mathrm{Mo},W\right\},B=\left\{S,\mathrm{Se}\right\},0x,y0.1.$

3. The doped TMD of claim 1, wherein the doped TMD is a p-doped TMD and has the following formula: $A_{\left(1-x\right)}{M}_x{B}_{\left(2-y\right)}{X}_y;M=\left\{V,\mathrm{Nb},\mathrm{Ta},\mathrm{Ti},\mathrm{Zr},\mathrm{Hf}\right\},X=\left\{N,P,\mathrm{As},\mathrm{Sb}\right\},A=\left\{\mathrm{Mo},W\right\},B=\left\{S,\mathrm{Se}\right\},0x,y0.1.$

4. The doped TMD of claim 1, wherein the doped TMD is a n-doped TMD and has the following formula: $A{B}_2{Z}_z;Z=\left\{H,\mathrm{Li},\mathrm{Na},K\right\},A=\left\{\mathrm{Mo},W\right\},B=\left\{S,\mathrm{Se}\right\},0z0.1.$

5. The doped TMD of claim 1, wherein the doped TMD is a p-doped TMD and has the following formula: $A{B}_2{Z}_z;Z=\left\{N,P,\mathrm{As},F,\mathrm{Cl},\mathrm{Br},I\right\},A=\left\{\mathrm{Mo},W\right\},B=\left\{S,\mathrm{Se}\right\},0z0.1.$

6. The doped TMD of claim 1, wherein the doped TMD is said combination thereof.

7. The doped TMD of claim 2, wherein X is F.

8. The doped TMD of claim 2, wherein X is Cl.

9. The doped TMD of claim 2, wherein X is OH.

10. The doped TMD of claim 3, wherein X is N.

11. The doped TMD of claim 3, wherein X is P.

12. The doped TMD of claim 3, wherein M={Nb, Ta, Zr, Hf}.

13. The doped TMD of claim 3, wherein M={Nb, Ta, Zr, Hf} and X={N, P}.

14. The doped TMD of claim 13, wherein M is Nb.

15. The doped TMD of claim 13, wherein M is Ta.

16. The doped TMD of claim 13, wherein M is Zr.

17. The doped TMD of claim 13, wherein M is Hf.

18. The doped TMD of claim 4, wherein Z is H.

19. The doped TMD of claim 4, wherein Z is Li.

20. The doped TMD of claim 4, wherein Z is Na.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0048] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0049] Example embodiments of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which:

[0050] FIG. 1 is a graph showing the mobility () of electrons as a function of channel thickness (t.sub.CH), and illustrates that for Si on insulators (SOI), the mobility degrades when t.sub.CH is below 4 nm, while transition metal dichalcogenides (MoS.sub.2, WSe.sub.2, etc.) show robust mobility for thinner channels.

[0051] FIG. 2 shows a computational approach for determining dopants.

[0052] FIG. 3 shows graphs to determine candidates for substitution doping in the present disclosure.

[0053] FIGS. 4A-4B show larger versions of the graphs in FIG. 3.

[0054] FIG. 5 shows graphs to determine candidates for additional atom doping in the present disclosure.

[0055] FIGS. 6A-6B show larger versions of the graphs in FIG. 5.

[0056] FIG. 7 is a graph showing why a MoS.sub.2 monolayer can be used as a channel material in a proton based ECRAM.

[0057] FIG. 8 is a periodic table of the elements showing n-dopant candidates for TMDs.

[0058] FIG. 9 is a periodic table of the elements showing p-dopant candidates for TMDs.

[0059] FIG. 10 shows a comparison of pristine MoS.sub.2 with Cl doped MoS.sub.2 and Nb doped MoS.sub.2.

[0060] FIGS. 11A-11C show larger versions of the graphs of FIG. 10.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0061] As set forth above, the present disclosure provides a list of chemistries to n-dope and p-dope transition metal dichalcogenides (TMDs) (1) using substitution doping within the fractional limit 0x, y0.1 and/or (2) by adding elements to pristine TMD within the fractional limit 0z0.1. The list of elements for doping TMDs of the form AB.sub.2 where A={Mo, W}, B={S, Se} are: [0062] Substitution n-doping: A.sub.(1-x)M.sub.xB.sub.(2-y)X.sub.y; M={Re, Os}, X={F, Cl, Br, I, OH}; [0063] Substitution p-doping: A.sub.(1-x)M.sub.xB.sub.(2-y)X.sub.y; M={V, Nb, Ta, Ti, Zr, Hf}, X={N, P, As, Sb}; [0064] Additional atom n-doping: AB.sub.2Z.sub.z; Z={H, Li, Na, K}; [0065] Additional atom p-doping: AB.sub.2Z.sub.z; Z={N, P, As, F, Cl, Br, I}; and [0066] Combinations of the above lists.

[0067] As shown in FIG. 2, the Jellium (uniform e gas) approach is limited. In particular, the traditional defect formation calculations approach has unphysical charge distribution due to compensating background for charged defect.

[0068] In the present disclosure, screening is based on defect-band position relative to the pristine band edges, formation energy of substitution, and charge transition levels.

[0069] In a large cell (44) of monolayer MoS.sub.2 and WSe.sub.2 the present disclosure computes the band structure of pristine TMD as well as TMD with one substitution dopant (either metal replaced by another atom, or S replaced by another atom). The present disclosure also considers the case of adding atoms on TMDs. Additionally, the present disclosure also considers an OH radical occupying the S site as moisture is known to affect the properties of TMDs.

[0070] When the bands of the defect states (a) do not induce a mid-gap state (which can act as a scattering center), and (b) the hybridization of the defect bands leads to p-(n-) doping of TMDs where the TMD VBM (CBM) cross the Fermi level (EF), then these are labeled as potential candidates. Additionally, if the dopants do not lead to a significant band rearrangement, the present disclosure labels them as good candidates.

[0071] FIG. 3 shows graphs to determine candidates for substitution doping in the present disclosure, and FIGS. 4A and 4B show larger versions of those graphs. A CTL (charge transition level) of 0 or close to 0 in the graphs refers to ideal candidates for corresponding doping. As shown in FIG. 3, for A.sub.(1-x)M.sub.xB.sub.(2-y)X.sub.y where A={Mo, W} and B={S, Se}, suitable candidates for substitution n-doping include M={Re, Os} and X={F, Cl, Br, I, OH}, and suitable candidates for substitution p-doping include M={V, Nb, Ta, Ti, Zr, Hf} and X={N, P, As, Sb}.

[0072] FIG. 5 shows graphs to determine candidates for additional atom doping in the present disclosure, and FIGS. 6A and 6B show larger versions of those graphs. As noted above, a CTL of 0 or close to 0 in the graphs refers to ideal candidates for corresponding doping. As shown in FIG. 5, for AB.sub.2Z.sub.z where A={Mo, W} and B={S, Se}, suitable candidates for additional atom n-doping include Z={H, Li, Na, K}, and suitable candidates for additional atom p-doping include Z={N, P, As, F, Cl, Br, I}.

[0073] FIG. 7 is a graph showing why a MoS.sub.2 monolayer can be used as a channel material in a proton based ECRAM. That is, calculations according to the present disclosure explain why a MoS.sub.2 monolayer can be used as a channel material in proton based ECRAM: All group 1 elements can be used for this. That is, just like H, using {Li, Na, K} all should work for ECRAM applications.

[0074] FIG. 8 is a periodic table of the elements showing n-dopant candidates for TMDs. In the periodic table, green indicates a good candidate for n-doping, yellow indicates a potential candidate, and red indicates a candidate that is unlikely to n-dope. As can be seen from the periodic table in this figure, OH, halides, Re, Cr and Os are good candidates to potentially n-dope MoS.sub.2. Further, while sulfur point vacancies are moderately deep levels, ordered vacancies could n-dope TMDs. Thus, in the case of n-doping, for MoS.sub.(2-y)X.sub.y, X={OH, CI, Br, I, and potentially F}, or for Mo.sub.(1-x)M.sub.xS.sub.2, M={Re and potentially Cr, Os}

[0075] FIG. 9 is a periodic table of the elements showing p-dopant candidates for TMDs. In the periodic table, green indicates a good candidate for p-doping, yellow indicates a potential candidate, and red indicates a candidate that is unlikely to p-dope. As can be seen from the periodic table in this figure, V, Nb, and Ta are good candidates for p-doping MoS.sub.2. Further, Be, Sc, Ti, Zr, Hf, Zn, Al, Ga, In, Tl, Si, Ge, Sn and P could also p-dope MoS.sub.2. Thus, in the case of p-doping, for MoS.sub.(2-y)X.sub.y, X={potentially P}, or for Mo.sub.(1-x)M.sub.xS.sub.2, M={V, Nb, Ta, and potentially Be, Ti, Zr, Hf, Zn, Al, Ga, In, Tl, Si, Ge, Sn}.

[0076] FIG. 10 shows a comparison of pristine MoS.sub.2 with Cl doped MoS.sub.2 and Nb doped MoS.sub.2, and FIGS. 11A-11C show larger versions of the graphs in FIG. 10. In particular, FIG. 10 shows that compared to pristine MoS.sub.2, the Cl defect bands (a) has no in-gap state, and (b) hybridizes with the CBM leading to the bands crossing Fermi level (set to zero), resulting in n-doping of TMDs. Also, FIG. 10 shows that compared to pristine MoS.sub.2, the Nb defect bands (a) has no in-gap state, and (b) hybridizes with the VBM leading to the bands crossing Fermi level (set to zero), resulting in p-doping of TMDs.

[0077] The doped TMD in the present disclosure can be made by using typical growth methods like thermal oxidation, atomic layer deposition, pulsed laser deposition, chemical vapor deposition, plasma oxidation, wet anodization or other chemical treatments.

[0078] In the present disclosure, as the doping concentration is small (<10%), the negative effect on mobility of electrons is believed to be small.

[0079] The present disclosure computed the thermodynamic propensity to dope as well as the electronic structure change for the dopants. Applications include both doping channel materials in field effect transistors as well as modulating the I-V characteristic in electrochemical RAM applications.

[0080] That is, the present disclosure can be used to dope TMD channel layers in FET geometry. The same dopants if mobile can be used in ECRAM applications where the channel layer is a TMD.

[0081] In particular, the present disclosure can be used to improve existing transistor performance by integrating atomically thin 2D materials as channel layers.

[0082] The foregoing is illustrative of exemplary embodiments and is not to be construed as limiting the disclosure. Although a few exemplary embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in the above embodiments without materially departing from the disclosure.