Patent Application
20090263977
This disclosure relates in general to semiconductors and in particular to the selective functionalization of doped Group IV semiconductor surfaces.
Semiconductors form the basis of modern electronics. Possessing physical properties that can be selectively modified and controlled between conduction and insulation, semiconductors are essential in most modern electrical devices (e.g., computers, cellular phones, photovoltaic cells, etc.). Group IV semiconductors generally refer to those first four elements in the fourth column of the periodic table: carbon, silicon, germanium and tin.
The ability to deposit semiconductor materials using non-traditional semiconductor technologies such as printing may offer a way to simplify and hence reduce the cost of many modern electrical devices (e.g., computers, cellular phones, photovoltaic cells, etc.). Like pigment in paint, these semiconductor materials are generally formed as microscopic particles, such as nanoparticles, and temporarily suspended in a colloidal dispersion that may be later deposited on a substrate.
Nanoparticles are generally microscopic particles with at least one dimension less than 100 nm. In comparison to a bulk material (>100 nm) which tends to have constant physical properties regardless of its size (e.g., melting temperature, boiling temperature, density, conductivity, etc.), nanoparticles may have physical properties that are size dependent, such as a lower sintering temperature.
The nanoparticles may be produced by a variety of techniques such as evaporation (S. Ijima, Jap. J. Appl. Phys. 26, 357 (1987)), gas phase pyrolysis (K. A Littau, P. J. Szajowski, A. J. Muller, A. R. Kortan, L. E. Brus, J. Phys. Chem. 97, 1224 (1993)), gas phase photolysis (J. M. Jasinski and F. K. LeGoues, Chem. Mater. 3, 989 (1991)), electrochemical etching (V. Petrova-Koch et al., Appl. Phys. Lett. 61, 943 (1992)), plasma decomposition of silanes and polysilanes (H. Takagi et al, Appl. Phys. Lett. 56, 2379 (1990)), high pressure liquid phase reduction-oxidation reaction (J. R. Heath, Science 258, 1131 (1992)), etc.
A colloidal dispersion is a type of homogenous mixture consisting of two separate phases. A colloidal dispersion (or ink) generally consists of a continuous phase (such as a solvent), and a dispersed phase (generally particles under 1 um in diameter). The continuous phase must be compatible with the surface of the material to be dispersed. For example, carbon black particles (non-polar) tend to be easily dispersed in a hydrocarbon solvent (non-polar), whereas silica particles (polar) tend to be easily dispersed in alcohol (polar).
Polarity generally refers to the dipole-dipole intermolecular forces between the slightly positively charged end of one molecule to the negative end of another or the same molecule. However, semiconductor particles tend to be non-polar, and hence lyophobic (or solvent fearing).
It is often of benefit to functionalize semiconductor surfaces by the addition of capping agents in order to improve compatibility with the media and simplify and/or enable manufacturing processes. In general, a capping agent or ligand is a set of atoms or groups of atoms bound to a “central atom” in a polyatomic molecular entity. The capping agent is selected for some property or function not possessed by the underlying surface to which it may be attached.
Consequently, a common method of dispersing a non-polar particle in a polar solvent is through modification of the particle surface, often with an ionizable (or polar organic) capping agent or ligand. For example, ionizable functional groups, such as carboxyl, amino, sulfonate, etc. or polymeric forms thereof, are often covalently attached to non-polar particles in order to add charge and allow repulsive electrostatic forces aid in the dispersion of the particles in the solvent. Alternatively in the case of apolar solvents, non-ionizable organic groups, highly compatible with the solvent, may be covalently grafted to the particles to aid dispersion and impart stability via solvation forces. Examples of non-ionizable organic groups include different geometry hydrocarbons (e.g., alkanes, alkenes, alkynes, cycloalkanes, alkadienes, etc.).
In addition, once dispersed, these particles will tend to stay suspended and avoid agglomeration if the repulsive electrostatic and/or solvation forces are sufficiently higher than the normally attractive Van der Waals forces. If the repulsive barrier to Van der Waals interactions is higher than about 15 kT, then Brownian motion of the particles is too low to cause appreciable agglomeration and the dispersion is considered stable. This balance of energies is the essence of Detjaguin-Landau-Verwey-Overbeek (DLVO) theory used to explain stability of electrostatically-stabilized colloids.
Capping agents can also attach antimicrobial molecules (e.g., polycationic (quaternary ammonium), gentamycin, penicillin, etc.) on a Group IV semiconductor surface in order to protect people from microbial infection. For example, Group IV materials with antimicrobial capping agents may be used for making clothing that can be more safely worn in contaminated environments.
However, in these and other uses, it is generally difficult to selectively attach the capping agent to the Group IV semiconductor surface, since the surface's chemical structure tends to be uniform. Consequently, the capping agent tends to attach to all available surface sites reactive toward it, completely covering the surface. This may be problematic for applications which require a direct access to the Group IV semiconductor surface. For example, an excessive amount of capping agents may inhibit sintering. Sintering is generally a method for making objects from powder by heating the particles below their melting point until they adhere to each other.
In addition, once attached to the Group IV semiconductor surface, capping ligands may be difficult to remove and may consequently interfere with the surface functionality. For example, many capping agents (once deposited and sintered) may act as contaminants which detrimentally affect the electrical characteristics of the semiconductor particle.
In view of the foregoing, there is desired a method of selectively capping a semiconductor surface such that it still retains original surface properties.
The invention relates, in one embodiment, to a method of selectively attaching a capping agent to a Group IV semiconductor surface. The method includes providing the Group IV semiconductor surface, the Group IV semiconductor surface including a set of covalently bonded Group IV semiconductor atoms and a set of surface boron atoms. The method also includes exposing the set of boron atoms to a set of capping agents, each capping agent of the set of capping agents having a central atom and a set of functional groups, wherein the central atom includes at least a lone pair of electrons; wherein a complex is formed between at least some surface boron atoms of the set of surface boron atoms and the central atom of at least some capping agents of the set of capping agents.
The invention relates, in one embodiment, to a method of selectively attaching a capping agent to a Group IV semiconductor surface. The method includes providing the Group IV semiconductor surface, the Group IV semiconductor surface including a set of covalently bonded Group IV semiconductor atoms and a set of surface phosphorous atoms. The method further includes exposing the set of phosphorous atoms to a set of capping agents, each capping agent of the set of capping agents having a central atom and a set of functional groups, wherein the central atom includes at least a empty electron orbital; wherein a complex is formed between at least some surface phosphorous atoms of the set of surface phosphorous atoms and the central atom of at least some capping agents of the set of capping agents.
The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:
The present invention will now be described in detail with reference to a few preferred embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention.
As previously described, current methods of attaching a capping agent to a Group IV semiconductor surfaces are not selective because of non-selective surface reactivity and may be problematic for specific applications. In an advantageous manner, incorporation of atoms other than Group IV on a semiconductor surface may create these necessary selective anchor points. For example, Group III or Group V atoms, which are often used for semiconductor doping, may be incorporated. Dopants are added to a semiconductor in order to alter its electrical behavior. The addition of relatively small amounts of dopants (<1%), can change the electrical conductivity of the semiconductor by many orders of magnitude by increasing the amount of electrically charged carriers. Conduction generally refers to the movement of electrically charged carriers, such as electrons or holes (i.e., lack of electrons). Depending on the kind of impurity, a doped region of a semiconductor can have more electrons (n-type) or more holes (p-type). A typical p-type dopant is boron (Group III), which lacks an outer-shell electron compared with silicon and thus tends to contribute a hole to the valence energy band. In contrast, a typical n-type dopant is phosphorous (Group V), which has an additional outer-shell electron compared with silicon and thus tends to contribute an electron to the conduction energy band.
Boron (and other Group III) atoms with three electrons in outer shell in sp3 configuration carry one empty electron orbital which acts as electron acceptor. In contrast, Phosphorous (and other Group V) atoms with five outer shell electrons, in sp3 configuration have one electron orbital with a pair of electrons, which are available for electron donation. Because of such specific electron configurations, Group III atoms exhibit Lewis acid properties (acceptor of electron pair), while Group V atoms act as Lewis bases (donor of electron pair). Consequently, they can be used as selective attachment sites for capping agents with Lewis base/Lewis acid properties.
Referring now to
Referring to
Referring to
Consequently, the inventors believe that capping agents with electron pair donors (tertiary amines, phosphines, ethers, alcohols, sulfides, thiols, etc.) may be used for selective attachment to Group III dopant atoms, whereas capping agents with electron pair acceptors (boranes, aluminum trichloride and organochlorides, etc.) may be used for selective attachment to Group V dopant atoms such as phosphorous.
Silicon is located in the periodic table immediately below carbon. It has the four electrons available in its outer shell for bonding (2 electrons in the 3s orbital and 2 electrons in the 3p orbital). The s and p orbitals hybridize to form four sp3 orbitals. This allows a lower energy state to be achieved in a silicon atom by filling all the s and p orbitals in the outer silicon shell (3s2 and 3p6) when bonded to four of its neighbors. Thus, Si is tetravalent and forms tetrahedral compounds. Unlike carbon silicon does not form stable double bonds because of larger atom radius limiting overlap of two π-orbitals. In general, bonds with electronegative elements are stronger with silicon than with carbon.
Referring now to
Here, in internal lattice site 202 of nanoparticle or crystalline wafer, a silicon atom 202 is bonded to its four proximate silicon atom neighbors.
Similarly, on a surface lattice site 204 two Sp3 orbitals of silicon atom 204 used for bonding with neighboring silicon atoms and other two sp3 orbitals bound to neighboring hydrogen atoms. As previously described, these hydrogen atoms serve to passivate the silicon atom.
Referring now to
Dopant atoms that are substitutionally positioned in a lattice, provide an additional electron (in the case of an n-type dopant) or the lack of an electron (or hole in the case of a p-type dopant) generally available for electrical current transport. For example, in the case of an n-type dopant, five outer shell electrons are available (2 electrons in the outer orbital and 3 electrons in the outer p orbital). As only four are needed to form Sp3 hybrid orbital bonds with neighboring atoms, such as Si or H, an additional unbonded electron is available. In contrast, in the case of a p-type dopant, three outer shell electrons are available (2 electrons in the outer s orbital and one electron in the outer p orbital). Again, as four are needed to form Sp3 hybrid orbital bonds with neighboring semiconductor atoms, but only three electrons are available, one of the bonds is only partially filled, leaving a hole. In general, non-surface substitutional dopant atoms physically are not available as selective anchor points for Lewis acid/Lewis base capping agents because the capping agent molecules are generally larger than the lattice structure spacing.
In contrast, surface substitutional dopant atoms, such as 304, are available as selective anchor point because they are accessible to the corresponding active atom of the capping agent. Here, R 304 is bonded to two semiconductor atoms, such as Si, and a passivating atom, such as H.
In the case of a p-type dopant (Group III atom), as previously described, three outer shell electrons are generally available. Here, the surface substitutional dopant in sp3 hybridization state has four sp3 orbitals: three bonding sp3 orbitals, each carrying one unpaired electron, and fourth non-bonding empty sp3 orbital. Consequently, Group III atom R 304 is bonded via three bonding sp3 orbitals with three neighboring atoms: two Si atoms and an H atom, leaving fourth empty sp3 orbital available to accept extra electron pair. Consequently, 304 may function like a Lewis acid when complexing with a Lewis base (electron pair donor).
By analogy, in the case of an n-type dopant (Group V atom), five outer shell electrons are generally available. Here, the surface substitutional dopant in sp3 hybridization state has four sp3 orbitals: three bonding sp3 orbitals, each carrying one unpaired electron, and fourth non-bonding sp3 orbital with a free electron pair available for electron donation. Thus, 304 may function like a Lewis base when complexing with a Lewis acid via donation of its free electron pair.
Referring now to
Aryl generally refers to any functional group or substituent derived from a simple aromatic ring. An alkyl is a univalent (or free) radical containing only carbon and hydrogen atoms where all carbon-carbon bonds are single bonds. Straight chain and branched alkyls form a homologous series with the general formula CnH2n+1. Examples include methyl, CH3 (derived from methane), isopropyl C3H7 (derived from isopropane), and butyl C4H9 (derived from butane). Cyclic alkyls (derived from cycloalkanes) have two less hydrogens and therefore general formula CnH2n−1. Examples include cyclopentyl C5H9 and cyclohexyl C6H11 They are normally not found on their own but are found as part of larger branched chain or cyclic organic molecules. On their own they are free radicals and therefore extremely reactive.
Initially, at 402, surface substitutional boron atom is exposed to the tertiary amine (all three hydrogen groups replaced with substitutants). Tertiary amines have three Alkyl/Aryl functional groups attached to the nitrogen atom via N—C bonds.
Consequently, at 404, the free electron pair of the fourth non-bonding sp3 orbital of Nitrogen atom is placed on the empty sp3 orbital of a Lewis base receptor Boron atom to form a complex, as described above. This electron pair is weakly shared between the nitrogen and the boron, rather than forming a much stronger covalent bond, since the binding energy of the complex is less than the binding energy (BE) with the tertiary amine functional groups: BE of B—N bond is 389 kJ/mol, while BE of N—C bond is 754.3 kJ/mol. Consequently, this complex bond between Boron and tertiary amine may be temporary. That is, the addition of energy, such as heat, will generally destroy the complex before breaking N—C bonds with the functional groups.
Initially, at 406, a surface substitutional boron atom is exposed to the tertiary amine with at least one hydrogen functional group. As before, in 408 a complex begins to form between the nitrogen and the boron. However, binding energies of B—H and N—H groups (340 and 339 kJ/mol respectively) are lower than B—N bond (389 kJ/mol). Because of that soon thereafter at 410, these B—H and N—H bonds weaken, a hydrogen atom in a functional group interacts with a nearby surface hydrogen atom and form H2 (hydrogen gas), which is subsequently vented. In the result, coordinate bond between Boron and Nitrogen at 412 becomes coordinate covalent bond, Thus, interaction of Boron with primary and secondary amines generally results into permanent attachment of the amine molecule.
Referring now to
Initially, at 502, surface substitutional boron atom is exposed to the tertiary phosphine. Consequently, at 504 the free electron pair of the fourth non-bonding sp3 orbital of Phosphorus atom is placed on the empty sp3 orbital of a Lewis base receptor Boron atom 504 to form a complex, as described above. This electron pair is weakly shared between the phosphorus and the boron, rather than forming a much stronger covalent bond, since the binding energy of the complex is less than the binding energy (BE) with the tertiary phosphine functional groups: BE of B—P bond is 346.9 kJ/mol, while BE of P—C bond is 513.4 kJ/mol. Consequently, this complex bond between Boron and tertiary phosphine may be temporary. That is, the addition of energy, such as heat, will generally destroy the complex before breaking P—C bonds with the functional groups.
Initially as before, at 506 a complex begins to form between the phosphorus and the boron. However, binding energies of B—H and P—H groups (340 and 297 kJ/mol respectively) are lower than B—P bond (346.9 kJ/mol). Because of that soon thereafter at 508, these B—H and P—H bonds weaken, a hydrogen atom in a functional group interacts with a nearby surface hydrogen atom and form H2 (hydrogen gas), which is subsequently vented. In the result, coordinate bond between Boron and Phosphorus at 510 becomes coordinate covalent bond 512. Thus, interaction of Boron with primary and secondary phosphines results into permanent attachment of the phosphine molecule.
Referring now to
Initially, at 602, surface substitutional boron atom is exposed to the ether. Consequently, at 604, one of two free electron pairs may then form a complex with the empty sp3 orbital of a boron atom, as described above. This electron pair is weakly shared between the oxygen and the boron, rather than forming a much stronger covalent bond, since the binding energy of the complex is less than the binding energy (BE) with the ether functional groups: BE of B—O bond is 808.8 kJ/mol, while BE of O—C bond is 1076.5 kJ/mol. Consequently, this complex bond between Boron and the ether may be temporary. That is, the addition of energy, such as heat, will generally destroy the complex before breaking O—C bonds with the functional groups.
Initially, at 606, a surface substitutional boron atom is exposed to the alcohol. As before, in 608 a complex begins to form between the oxygen and the boron. However, binding energies of B—H and O—H groups (340 and 427.6 kJ/mol respectively) lower than B—O bond (808.8 kJ/mol). Because of that soon thereafter at 608, these B—H and O—H bonds weaken, a hydrogen atom of a functional group interacts with a nearby surface hydrogen atom and form H2 (hydrogen gas), which is subsequently vented. In the result, coordinate bond between Boron and oxygen at 610 becomes coordinate covalent bond 612. Thus, interaction of Boron with alcohols results into permanent attachment of the alcohol molecule
It has to be noted that although both alcohols and ethers are much more reactive toward B—H sites on H-passivated semiconductor surface than toward to the surface itself (Group IV-Group IV and Group IV—H bonds), they may interact with the surface itself, especially at elevated temperatures. Thus, ethers and alcohols are less selective Lewis Base reagents than amines and phosphines discussed above and sulfur compounds which will be discussed below.
Referring now to
Initially, at 702, surface substitutional boron atom is exposed to the sulfide.
Consequently, at 704, one of two free electron pairs may then form a complex with the empty sp3 orbital of a boron atom, as described above. This electron pair is weakly shared between the sulfur and the boron, rather than forming a much stronger covalent bond, since the binding energy of the complex is less than the binding energy (BE) with the sulfide functional groups: BE of B—S bond is 580.7 kJ/mol, while BE of S—C bond is 714.1 kJ/mol. Consequently, this complex bond between Boron and the sulfide may be temporary. That is, the addition of energy, such as heat, will generally destroy the complex before breaking S—C bonds with the functional groups.
Initially, at 606, a surface substitutional boron atom is exposed to the thiol. As before, in 708 a complex begins to form between the sulfur and the boron. However, binding energies of B—H and S—H groups (340 and 344.3 kJ/mol respectively) lower than B—S bond (580.7 kJ/mol). Because of that soon thereafter at 708, these B—H and S—H bonds weaken, a hydrogen atom of a functional group interacts with a nearby surface hydrogen atom and form H2 (hydrogen gas), which is subsequently vented. In the result, coordinate bond between Boron and sulfur at 710 becomes coordinate covalent bond 712. Thus, interaction of Boron with thiols results into permanent attachment of the thiol molecule.
Referring now to
Generally, dynamic light scattering quantifies the particle size distribution by measuring the power spectrum of frequency shifted, scattered light arising from random thermal (Brownian) motion of the suspended particles. These frequency (Doppler) shifts are related to the particle velocities, where smaller particles generally have higher velocities and therefore larger Doppler shifts. In the heterodyne method employed here, a coherent laser light source is directed at the suspension of particles, and the frequency-shifted, back-scattered light due to particle motions is recombined with part of the incident, unshifted light. The resulting interference pattern relates to the distribution of Doppler shifts. Thus, particle size distribution is obtained by analysis of the detected heterodyne power spectrum.
Horizontal axis shows particle agglomerate size (average size for that bin or “channel”) in a logarithmic nanometer (nm) scale, while vertical axis shows % channel (e.g., the percentage of particles in the size range of that channel). In general, in colloidal dispersions of nanoparticles, the particles tend to form agglomerates in order to reduce their surface energy. Agglomerates may comprise relatively weak bonds between the nanoparticles (i.e., a potential energy minimum on the order of a few kT), and can be easily disassociated with the addition of small mechanical or thermal energy. Thus, in general, the larger the size of underlying nanoparticle, the larger the corresponding size of the agglomerate.
A first reference colloidal dispersion 802 is loaded with un-doped Si nanoparticles capped with a C1-8 hydrocarbon. A second colloidal dispersion 804 loaded with boron-doped Si nanoparticles partially capped with a primary amine (i.e., an amine with a single non-hydrogen functional group and two hydrogen functional groups). A third colloidal dispersion 806 is loaded with boron-doped Si nanoparticles partially capped with a tertiary amine (i.e., an amine with a three non-hydrogen functional groups). A fourth colloidal dispersion 808 is loaded with boron-doped Si nanoparticles partially capped with a sulfide. And a fifth colloidal dispersion 810 is loaded with boron-doped Si nanoparticles in an inert solvent, and thus uncapped
Capping reagent is also a solvent for all these p-type particle's dispersions. Un-doped C18-capped particles are dispersed in chloroform. Inert solvent is a mixture of chloroform and benzene.] Particles and solvent(s) were mixed and the mixture was stirred for 30 min by stirring at room temperature followed by about a 15 min ultrasonic horn sonication at about 15% power. The colloidal dispersions (except the one in inert solvent) were further filtered through 5 micron Nylon filter.
In general, for a particle in a solvent, the percentage of capped surface area is substantially correlated to the degree of dispersability. That is, highly capped particles disperse well, while lightly capped or uncapped particles disperse poorly and tend to clump and precipitate out of the solvent.
In the first reference colloidal dispersion 802, in which C18 hydrocarbon capping ligands are attached to the silicon surface atoms in the nanoparticle, the dispersion quality is very good, with an average agglomerate size of about 11 nm corresponding to a single particle size. In contrast, in the fifth colloidal dispersion 810, in which uncapped nanoparticles are suspended in an inert solvent, the dispersion is poor, with an average agglomerate particle size of about 1100 nm. Consequently, second colloidal dispersion 804, third colloidal dispersion 806, and fourth colloidal dispersion 808, in which the capping agents complex with surface substitutional boron atoms, dispersability is better than with the fifth non-capped inert solvent colloidal dispersion, but worse than the first C-18 capped solvent colloidal dispersion. Among themselves, second colloidal dispersion 804 with primary amine partial capping is characterized by smaller average agglomerate size than third colloidal dispersion 806 and fourth colloidal dispersion 808.
Referring now to
In general, Fourier transform infra-red (FTIR) spectroscopy is a measurement technique whereby spectra are collected based on measurements of the temporal coherence of a radiative source, using time-domain measurements of the electromagnetic radiation or other type of radiation (shown as wavenumber on the horizontal axis). At certain resonant frequencies characteristic of the specific sample, the radiation will be absorbed (shown as absorbance A.U.) on the vertical axis) resulting in a series of peaks in the spectrum, which can then be used to identify the samples. A set of peaks in the range 2850-3000 cm−1 is representative of a hydrocarbon bonds present in capping ligands on the particle's surface.
Here, a set of porous thin film compacts were formed by depositing a colloidal dispersion of p-type silicon nanoparticles on FTIR transparent substrates. These thin films were then baked at about 60-350° C. from 5 to 30 minutes, in order to remove any remaining solvent and complexed capping agents. Five sets of porous compacts in total were made: C8 hydrocarbon capped 902, primary amine capped 804, tertiary amine capped 806, sulfide capped 808, and non-capped 810. These porous compacts were then measured using FTIR as described above.
FTIR spectra of dried films printed from several colloidal dispersions were normalized by Si—Si signal intensity (˜640 cm−1). Thus, the intensity of hydrocarbon peaks in the range 2850-3000 cm−1 becomes a reflection of the degree of permanent capping with various capping agents. As it can be seen, the C8 hydrocarbon capped 902 and primary amine capped 804 show set of intense peaks in the range 2850-3000 cm−1 characteristic of hydrocarbon absorption, whereas for the remaining dry films 806, 808 and 810 this characteristic organic peak is negligible intensity. It is believed that in dispersion 902 the surface of particles is uniformly capped with C8 hydrocarbons chains via permanent covalent bonding. Dried film deposited from this dispersion has most intense hydrocarbon peak. For dispersion 804, where primary amine was applied and also formed permanent covalent bonds with the surface of particles (because of hydrogen gas formation as previously described), the hydrocarbon peak was observed as well. However it has 3-4 times lower intensity than the one for C8 capped particles. This difference in hydrocarbon peak intensities confirms partial capping of Si nanoparticles surface with primary amine, which selectively interact with boron sites on p-type particle's surface. As it was shown earlier, for the dispersions 806 and 808 where the nanoparticles were treated with tertiary amine and sulfide respectively, due to Lewis Acid/Lewis Base complex formation between the surface boron atoms and dispersant an average aggregate size is much smaller than for the dispersion 810 in the inert solvent (
Referring to now to
Here, the appropriate colloidal dispersion was deposited as a film on dielectric (quartz) substrate. The film was then dried on pre-bake step (at about 60-350° C. from about 5 minutes to about 30 minutes) in order to form a porous compact, as well as remove solvents and capping agents. The porous compact was then heated (at between about 800° C. to about 1000° C. and for about 10 seconds to about 10 minutes) in order to sinter the nanoparticles into a densified film on to which the probes are placed. Consequently, it is believed that the lacking selectivity, the bonded capping agents reduce sinterability and hence conductivity.
As shown in
For the purposes of this disclosure and unless otherwise specified, “a” or “an” means “one or more.” All patents, applications, references and publications cited herein are incorporated by reference in their entirety to the same extent as if they were individually incorporated by reference. In addition, the word set refers to a collection of one or more items or objects. Furthermore, the inventors believe that similar to p-type Group IV semiconductor surfaces selective capping via interaction of surface boron atoms with capping ligands of LB nature, n-type Group IV semiconductor surfaces can be selectively capped via interaction of surface phosphorus atoms with capping ligands of LA nature such as boranes, aluminum chlorides and organochlorides, etc. In addition, the set of functional groups may have a linear configuration, a branched configuration, or a cyclic configuration.
The invention has been described with reference to various specific and illustrative embodiments. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention. Advantages of the invention include the selective functionalization of doped Group IV nanoparticle surfaces.
Having disclosed exemplary embodiments and the best mode, modifications and variations may be made to the disclosed embodiments while remaining within the subject and spirit of the invention as defined by the following claims.
