Systems and methods for storing molecular diborane

Abstract

A method and system for storing diborane is described by adsorbing diborane onto a microporous carbon adsorbent that contains slit pores between the graphite layers at intervals between the graphite layers that increase the activation energy required for diborane decomposition relative to the activation energy for decomposition of unadsorbed gaseous diborane.

Description

[Technical field]

[0001] The following description is in the field of adsorption media and methods for adsorbing diborane onto the adsorption media for adsorptive storage. [Background technology]

[0002] Diborane (B2H6) is commonly used as a source gas (or "reagent gas") in industrial processes, for example, in the manufacture of semiconductor and microelectronic devices. In one specific example, diborane is used as a raw material in chemical vapor deposition (CVD) processes, such as growing thin doped silicon layers or conformal boron nitride coatings. Diborane is also used in ion implantation applications.

[0003] Diborane is supplied to the process as a reagent gas in a useful gas form and must contain very low levels of contaminants. Typically, diborane is dispensed from a storage vessel which contains the diborane in a chemical form that allows it to be reliably dispensed from the storage vessel.

[0004] One method of storing diborane is storage in a pressurized vessel, such as a pressurized cylinder. Diborane can be stored and delivered in its pure form at very high concentrations, such as concentrations approaching 100 percent diborane. The challenge with these systems, however, is that concentrated diborane is very unstable at room temperature and will chemically decompose into the reactive BH3 compound, which can further react to form hydrogen (H2) and more stable higher borane compounds, such as B4H. 10 , B5H9, or B 10 H 14 Pure diborane held under pressure will rapidly decompose to substantially lower concentrations within a few days or weeks.

[0005] To improve stability, diborane may be stored mixed with an inert gas, such as gaseous hydrogen (H2), nitrogen (N2), or argon, at a diborane concentration of up to 30 percent, but typically at diluted concentrations ranging from 1 to 10 percent diborane. Storing diborane in a mixture with an inert gas reduces the decomposition rate of diborane, which decomposes at a rate inversely proportional to the concentration of diborane in the mixture. The low concentration of diborane in the mixture reduces the decomposition rate of diborane. Nevertheless, these mixtures may have a short shelf life of 6 or 12 months, which limits the value of the mixture.

[0006] To further improve the stability of diborane, the temperature of the stored mixture of diborane and inert gas can be reduced. However, refrigeration adds significant complexity and expense to the process of transporting, storing, and distributing stored diborane. To best improve stability, the diborane and inert gas must all be packed in a pressurized cylinder under refrigerated conditions, then transported, stored, and ultimately connected to the process tool. The cylinder must be refrigerated throughout its entire life from manufacture to use, including the time that the cylinder is connected to the process tool to deliver diborane to the process tool.

[0007] As an alternative means for storing and delivering reagent gases, certain reagent gases may be adsorbed, optionally under pressure, onto a solid adsorbent medium held in a storage vessel and selectively desorbed for delivery from the vessel. Desorption of the reagent gas and delivery from the storage vessel may involve application of reduced pressure, application of thermal energy, or both.

[0008] Methods for storing diborane using solid adsorbents have been investigated (see, for example, Patent Documents 1 to 4), which are usually based on the reactive adsorption of BH3 species to Lewis base sites. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Pat. No. 3,928,293 [Patent Document 2] U.S. Pat. No. 4,223,173 [Patent Document 3] U.S. Pat. No. 5,993,776 [Patent Document 4] U.S. Pat. No. 1,094,0426 Summary of the Invention [Problem to be solved by the invention]

[0010] Although there is strong commercial interest in sorbent-type 100% diborane gas storage and delivery products, no successful commercial products have been developed. Cryogenic storage of diborane is perhaps the most viable solution, but cryogenic storage has not been fully adopted commercially by users due to the complexities and costs associated with long-term storage at very low temperatures.

[0011] It is highly desirable to identify an adsorption medium that is effective to adsorb diborane in a reversible (desorbable) manner in order to store diborane in a chemically stable state, preferably with good stability of the diborane during storage. [Means for solving the problem]

[0012] The following description relates to systems and methods for reversibly storing diborane on a sorbent. In one aspect, the present disclosure relates to a container for storing diborane, the container comprising a container interior and a microporous carbon adsorbent within the container, the diborane within the container being at least partially adsorbed on the microporous adsorbent, the microporous adsorbent comprising slit pores between the graphite layers at the graphite layer spacings, the slit pores increasing the activation energy required for decomposition of diborane relative to the activation energy for decomposition of unadsorbed gaseous diborane at ambient pressure and the same temperature.

[0013] In another aspect, the invention relates to a method for reversibly storing diborane on an adsorbent in a container, the method comprising adding diborane gas to a storage container comprising a microporous carbon adsorbent including slit pores between graphite layers having a graphite layer spacing that increases the activation energy required for decomposition of diborane relative to the activation energy for decomposition of unadsorbed gaseous diborane, such that diborane is adsorbed onto the microporous carbon adsorbent, and storing the adsorbed diborane in the container. [Brief description of the drawings]

[0014] [Figure 1A] 1 shows a diborane molecule in storage. [Figure 1B] 1 shows a diborane molecule in storage. [Figure 1C] 1 shows a diborane molecule in storage. [Figure 2A] The activation energies for the reactions involved in the chemical decomposition of diborane are shown below. [Figure 2B] The activation energies for the reactions involved in the chemical decomposition of diborane are shown below. [Figure 2C] The activation energies for the reactions involved in the chemical decomposition of diborane are shown below. [Diagram 3] 1 illustrates an exemplary storage and delivery vessel as described. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Described below are systems, products, and methods useful for reversibly storing adsorbed diborane using carbon adsorbents. Diborane is a compound composed of two boron atoms and six hydrogen atoms, with the chemical formula B2H6. Diborane is used, for example, as a reagent gas in the semiconductor industry, as a feed material in boron doping applications, and as a reducing agent in tungsten deposition.

[0016] According to the present disclosure, diborane may be stored by being adsorbed on the surface (specifically the pores of the surface) of a carbon adsorbent contained within a storage vessel. The storage vessel contains activated carbon, adsorbed diborane, and usually a quantity of gaseous diborane in equilibrium with the adsorbed diborane. That is, the vessel contains an adsorbed phase of diborane in equilibrium with the gas phase of diborane. The adsorbed diborane is reversibly adsorbed on the adsorbent surface and can be stored in this adsorbed state for a period of time within the vessel and selectively desorbed from the surface in a controlled manner for dispensing from the storage vessel. The desorbed diborane can be delivered from the storage vessel, preferably with low levels of contaminants, for use as a gaseous raw material for industrial processes, for example for the manufacture of semiconductor or microelectronic devices.

[0017] Diborane can be stored in concentrated form, meaning that the storage vessel contains activated carbon adsorbent, adsorbed phase diborane and gas phase diborane, and any other gaseous or adsorbed chemicals, such as inert gases, in small or less amounts to stabilize the diborane. Diborane may be optionally stored in combination with an inert gas, such as argon, nitrogen, or hydrogen, but the inert gas is not necessary to stabilize the stored diborane and may be omitted from the vessel. In useful or preferred systems, the vessel contains at least 60 percent, 70, 80, 90, 95, 99, or 99.9 percent (atomic) diborane, based on the total content of gaseous and adsorbed species. The vessel may contain less than 40, 30, 20, 5, 1, or 0.1 percent (atomic) of non-borane species in the gas or adsorbed phase (excluding the carbon adsorbent).

[0018] The diborane is adsorbed in the vessel onto the surface of a carbon adsorbent, including an activated carbon adsorbent. The term "carbon adsorbent" refers to a variety of carbon-based materials derived synthetically from carbon-containing polymeric materials or from naturally derived carbon-based materials. Examples include carbon formed by pyrolysis of synthetic hydrocarbon resins such as polyacrylonitrile, sulfonated polystyrene-divinylbenzene, polyvinylidene chloride, etc.; cellulosic char; activated carbon formed from charcoal, as well as naturally derived materials such as coconut shells, pitch, wood, petroleum, coal, etc.; nanoporous carbon, etc.

[0019] Carbon adsorbents that may be particularly useful in the described methods or storage systems may be those that have a high degree of purity and contain a small amount of chemical defects on the graphite layers of the adsorbent, which have a low concentration of chemical functional groups attached to the graphite sheets, a small amount of missing and unsaturated carbon atoms, a small amount of metal impurities, a small amount of closed pores, and a small amount of non-parallel graphite layers that create wedge-shaped pores.

[0020] Carbon adsorbents are known to be highly porous adsorbent materials with a complex chemical structure of predominantly carbon atoms. Activated carbon adsorbents can be in the form of a solid material that contains a network of pores present in a rigid matrix of layers of carbon atoms, i.e., layers of "graphite," which are stacked and linked together by chemical bonds to create a highly porous structure of interconnected openings or channels, called "pores," between the graphite layers.

[0021] Non-limiting examples of useful carbon adsorbents include carbon-based adsorbents formed by pyrolysis of synthetic polymers such as hydrocarbon, halocarbon (e.g., chlorocarbon), or hydrohalocarbon resins, e.g., polyacrylonitrile, polystyrene, sulfonated polystyrene-divinylbenzene, polyvinylidene chloride (PVDC); polymer framework (PF) materials; porous organic polymers (POPs); cellulosic chars; charcoal; and activated carbons formed from naturally derived materials such as coconut shells, pitch, wood, petroleum, and coal.

[0022] The carbon sorbent may have any suitable form, such as, for example, that of granules (also called "particles"). Granules are individual pieces of activated carbon sorbent, each piece having a relatively small size, for example, less than 2 centimeters, or less than 1 or 0.5 centimeters. The particles may have any useful particle size, shape, and size range. Exemplary shapes include beads, granules, pellets, tablets, shells, saddles, powders, irregularly shaped particles, extrudates of any shape and size, fabric or web-form materials, honeycomb matrix monoliths, and composites (of sorbent with other components), as well as crushed or crushed forms of the sorbent materials of the types previously described.

[0023] Useful or preferred carbon sorbent particles can have an average size ranging from 0.5 to 20 millimeters, e.g., 1 to 15 or 1 to 10 millimeters (mm). The average particle size of a population of sorbent particles can be measured by standard techniques, including randomly selecting particles from the population of particles and measuring the size (e.g., diameter) with the use of a micrometer.

[0024] Carbon adsorbents (e.g., in the form of particles or as a monolith) can be characterized by the surface area of ​​the adsorbent. Surface area measurements can be performed by known methods, for example by applying BET analysis of nitrogen adsorption isotherms. According to useful or preferred examples, activated carbon adsorbent materials can exhibit a relatively high surface area, for example a surface area of ​​at least 500, 600, or 700 square meters per gram, for example a surface area in the range of 700 to 1000 square meters per gram, or even higher.

[0025] Another characteristic of a carbon adsorbent is its porosity (sometimes referred to as "pore volume"), which is the volume in the activated carbon adsorbent occupied by pores per mass of the adsorbent. Exemplary activated carbon adsorbent particles may have a porosity of at least 0.2 milliliters per gram, e.g., at least 0.5 milliliters per gram, and preferably at least 0.8 milliliters per gram.

[0026] Carbon adsorbents are porous and contain an interconnected network of pores that extend from the surface to the interior of the adsorbent particle. The pore sizes of adsorbent materials are classified into general ranges based on the average pore size of the adsorbent particle aggregate. Activated carbon adsorbents with an average pore size greater than 50 nanometers (nm) are typically referred to as macroporous. Activated carbon adsorbents with an average pore size in the range of 2 to 50 nanometers (nm) are typically referred to as mesoporous particles. Carbon adsorbents with an average pore size less than 2 nanometers are typically referred to as microporous. These terms are defined by IUPAC terminology.

[0027] Carbon adsorbents may have pores in the macroporosity range, pores in the mesoporosity range, and pores in the microporosity range. Desirably, for useful adsorption of diborane as described, the adsorbent may have a useful amount of pores in the microporosity range. Specifically, the described storage methods and systems have been found to be effective using carbon-based adsorbents containing pores, which are referred to as "slit pores" and have sizes that provide improved chemical stability of diborane that applicants have identified as being related to the energy levels of diborane molecules contained in slit pores of a particular size range.

[0028] Carbon adsorbents are believed to have a pore morphology known as "slit pores." In activated carbon adsorbents, the solid adsorbent material on a molecular scale comprises parallel sheets of graphite. The spaces or openings that exist between adjacent graphite sheets are the "pores" of the adsorbent and act as storage spaces for chemical molecules in an "adsorbed" state. These pores can be characterized by the distance or "spacing" of adjacent graphite layers, which is one of the three size dimensions of the three-dimensional pores of the adsorbent.

[0029] As determined by the applicant, the chemical stability of diborane stored in an adsorbed state in the slit pores of a carbon adsorbent is affected by the spacing of the graphite layers forming the pores, the value of which is referred to as the "graphite layer spacing" of the slit pore. The stability and chemical decomposition rate of the stored diborane molecules will be greater or less based on the size of the slit pore, measured by the distance between the adjacent graphite layers forming the slit pore. As determined by the applicant, diborane molecules stored in slit pores having a graphite layer spacing of less than 0.8 nanometers, preferably less than 0.7 nanometers, have improved stability, i.e., undergo reduced chemical decomposition, compared to diborane molecules stored in slit pores having a graphite layer spacing of more than 0.8 nanometers.

[0030] More specifically, the chemical decomposition of diborane occurs when the diborane molecule reacts to produce B3H9, B4H 10 , B5H9, or B 10 H 14 The initial reaction causes diborane (B2H6) to dissociate into two reactive borane (BH3) molecules. The borane molecule can then react with another diborane (B2H6) molecule to form other reactive intermediates such as B3H9 and B3H7, resulting in B4H 10 This results in relatively more stable boranes such as boranes and H2. For example,

[0031]

number

[0032] Computational Study of the Initial Stage of Diborane Pyrolysis Baili Sun and Michael L.McKe.Inorg.Chem.52,5962(2013). The improved level of chemical stability of the stored diborane is measured as the reduced chemical decomposition rate of the stored diborane, e.g., diborane contained within the pores of the adsorbent, compared to the chemical decomposition rate of unstored (unbound) gaseous diborane. These rates can be for storage and decomposition at any temperature, including ambient temperatures of 18-25 degrees Celsius, e.g., 21 or 23 degrees Celsius.

[0033] A reduction in the rate of chemical decomposition can be achieved by affecting the borane molecule in a way that reduces the rate constant for the forward reaction U1 (diborane dissociation), or U2 (BH3 attack on B2H6), or both. The rate constant k of the reaction is determined by the activation energy E a and temperature and is described by the Arrhenius equation: Thus, an increase in activation energy leads to a decrease in reaction rate or an increase in stability.

[0034]

number

[0035] Based on the following, it is shown that diborane can be stabilized, i.e., chemical decomposition of diborane can be reduced, by storing diborane molecules in an adsorbent having slit pores with a graphite layer spacing separation of less than 0.7 or 0.8 nanometers.

[0036] Referring to Figures 1A, 1B, and 1C, these figures show diborane molecules held in the slit pores of an adsorbent, such as an activated carbon adsorbent. Figures 1A, 1B, and 1C show diborane molecules contained in slit pores having graphite layer spacings of 1.0 nanometers, 0.8 nanometers, and 0.6 nanometers, respectively. Figure 1A shows a graphite layer spacing of 1.0 nanometers, which is also an approximation of the condition of gaseous diborane not constrained by any pore space of the adsorbent.

[0037] As the size of the slit pore decreases, for example, as the spacing of the graphite layers of the adsorbent becomes closer, the activation energy required for the decomposition of diborane to borane (BH3) drops sharply. See FIG. 2A. However, as the slit pore size decreases and the activation energy for the decomposition of diborane to borane decreases, the activation energy for the reaction of borane (BH3) with diborane (B2H6) increases more significantly and more substantially. See FIG. 2B. As shown in FIG. 2C, the combined effect of the decrease in the activation energy for the decomposition of diborane to borane and the increase in the activation energy for the reaction of borane (BH3) with diborane (B2H6) is that diborane chemically decomposes to B3H7 and then to B4H. 10 , B5H9, B 10 H 14 This is a significant increase in net activation energy at graphite layer spacings of about 0.7 and 0.8 nanometers when going to any higher order borane compound such as

[0038] The chemical decomposition of diborane involves multiple reaction pathways and includes reaction products that include various higher diboranes. One example of a reaction pathway produces B3H9. According to the described methods and systems, the carbon adsorbent used to store the adsorbed diborane can be selected to have slit pores with graphite layer spacing that increases the activation energy required for chemical decomposition of diborane adsorbed in the slit pores at a given temperature compared to the activation energy for decomposition of unadsorbed gaseous diborane at the same temperature. The activation energy to produce B3H9 is the sum of half the activation energy of reaction (i) plus the activation energy of reaction (ii), (i) B2H6 → 2BH3 (ii) B2H6+BH3→B3H9 It is.

[0039] Figures 2A, 2B, and 2C show data at a graphite layer spacing of 1.0 nanometer and at the "1 sheet" designation, with the "1 sheet" measurement representing the activation energy for decomposition of unadsorbed gaseous diborane. The graphs in Figures 2A, 2B, and 2C show Ovalene simulated pores at specific separations between the Ovalene sheets. The simulations used B97D / def2-TZVP / w06 with frozen surfaces level of theory.

[0040] A practical lower limit for the graphite layer spacing may be about 3.4 angstroms. Thus, preferred graphite layer spacing of adsorbents for storing and stabilizing diborane may range from 0.34-8.0 angstroms, e.g., 4.0, 5.0, or 6.0 angstroms, to 7.0, 7.5, or 8.0 angstroms. Useful or preferred adsorbents, e.g., carbon adsorbents, may have a useful or high relative amount of pores having graphite layer spacings within this range, e.g., may contain a total amount of pores with at least 50, 60, 70, or 80 percent of the pores being slit pores having graphite layer spacings in the range of 0.34-8.0 angstroms, e.g., 4.0-8.0 angstroms, or 5.0-8.0 angstroms, or 5.0, 5.5, or 6.0 angstroms to 7.0, 7.5, or 8.0 angstroms.

[0041] As used herein, graphite layer spacing can be determined by measuring adsorption isotherms using probe molecules such as nitrogen, argon, carbon dioxide, xenon, and the like. The described storage of diborane by reversible adsorption onto a sorbent having size characteristics as described can be carried out in a storage vessel of the type known for use in sorbent-based storage systems and methods. The vessel may be a rigid vessel having rigid side walls, a rigid top and bottom, and an opening at the top to which a valve or other dispensing device can be attached. The bottom may be generally flat, and the top may be flat, curved, rounded, domed, or elongated in shape. The side walls, bottom, and top are made of rigid materials such as metals (carbon steel, stainless steel, aluminum), fiberglass, or rigid polymers. To store the adsorbed diborane at low pressure in the vessel, the vessel does not need to be adapted to contain contents at high pressure.

[0042] The interior surfaces of the cylinder sidewall, top, and bottom may be finished in any suitable manner to microscopically reduce the true surface area resulting from uneven surface morphology, and may be treated to render the interior surfaces clean and non-reactive to ensure that the diborane is of high purity when dispensed from the container after a storage period. Examples of such finishes and treatments include abrasive blasting, polishing, grinding, sanding, electrolytic polishing, electroplating, electroless plating, coating, galvanizing, anodizing, and the like.

[0043] A "valve" may be any dispensing device that can be selectively opened and closed to allow the flow of gaseous diborane between the interior and exterior of the vessel. The valve may be of any type, such as a diaphragm valve. Various flow control devices, such as filters, pressure regulators, pressure gauges, flow regulators, etc., may be associated with the valve either inside or outside the vessel.

[0044] 1A-1C show an example of a fluid delivery system ("fluid delivery package") as described, in which a sorbent (e.g., activated carbon sorbent) is arranged for use in adsorbing, storing, and (upon desorption) dispensing diborane.

[0045] As shown, the fluid supply package 10 comprises a vessel 12 including a cylindrical wall 14 and a bed that enclose an interior volume 16 of the vessel 12 within which a sorbent 18 is disposed. The vessel 12 is joined at its upper end portion to a cap 20, which may have a flat feature on its periphery surrounding an upwardly extending boss 28 on its upper surface. The cap 20 has a central threaded opening that receives a correspondingly threaded lower portion 26 of a fluid distribution assembly.

[0046] The valve head 22 is movable between open and closed positions by any suitable operation, such as a manually operated hand wheel or a pneumatically operated activator 30 coupled thereto. The fluid distribution system includes an outlet port 24 for dispensing gaseous diborane from the fluid supply system when the valve is opened by operation of the hand wheel 30.

[0047] The sorbent 18 in the interior volume 16 of the vessel 12 may be of any suitable type disclosed herein and may include the sorbent, for example, in the form of a powder, particulate, pellet, bead, monolith, tablet, or other suitable form of activated carbon. The sorbent has an adsorptive affinity for diborane, allowing for adsorptive storage and selective distribution of diborane to the vessel interior. Distribution may be performed by opening the valve head 22 to accommodate desorption of diborane stored in adsorbed form on the sorbent and exhaust of gaseous diborane from the vessel through the fluid distribution assembly to an outlet port 24 and associated flow circuit (not shown), where the pressure at the outlet port 24 causes pressure-mediated desorption and exhaust of diborane from the fluid supply package interior. For example, the distribution assembly may be coupled to a flow circuit at a lower pressure compared to the pressure inside the vessel for such pressure-mediated desorption and distribution, for example, a subatmospheric pressure appropriate for a downstream tool coupled to the fluid supply package by the flow circuit. Optionally, dispensing may include opening valve head 22 in conjunction with heating of sorbent 18 to cause thermally mediated desorption of diborane for discharge from the fluid supply package.

[0048] The fluid supply package 10 can load diborane for storage on the sorbent by initially draining fluid from the interior volume 16 of the vessel 12 and subsequently flowing diborane into the vessel through outlet port 24, thereby serving the dual role of loading and dispensing gaseous diborane from the fluid supply package. Alternatively, the valve head 22 can include separate fluid introduction ports for filling the vessel with introduced fluid and loading the sorbent.

[0049] The diborane in the container may be stored at any suitable pressure condition, preferably sub-atmospheric pressure (less than 760 Torr) or low sub-atmospheric pressure (less than 100 Torr or less than 50 or 30 Torr), which enhances the safety of the fluid supply package relative to fluid supply packages such as high pressure gas cylinders.

Claims

1. 1. A container for storing diborane, comprising: Inside the container, a microporous carbon adsorbent within the container; diborane within the vessel at least partially adsorbed on a microporous adsorbent; The microporous adsorbent contains slit pores between the graphite layers at intervals between the graphite layers that increase the activation energy required for diborane decomposition relative to the activation energy for decomposition of unadsorbed gaseous diborane at ambient pressure.

2. 10. The vessel of claim 1, comprising a concentration of diborane of at least 50 percent (atomic), based on the total amount of adsorbed and gaseous species within the vessel.

3. the activation energy being the sum of half the activation energy of reaction (i) plus the activation energy of reaction (ii), (i)B ２ H ６ →2BH ３ (ii) B ２ H ６ +BH ３ →B ３ H ９ 2. The container of claim 1 .

4. 10. The container of claim 1, wherein the graphite sheets have a graphite layer spacing of 0.8 nanometers or less.

5. 10. The container of claim 1, wherein at least 50 percent of the pores of the adsorbent have a graphite interlayer spacing in the range of 0.4 to 0.8 nanometers.

6. 10. The container of claim 1, wherein at least 80 percent of the pores of the adsorbent have a graphite interlayer spacing in the range of 0.4 to 0.8 nanometers.

7. 10. The container of claim 1, wherein at least 80 percent of the pores of the adsorbent have a graphite interlayer spacing in the range of 0.4 to 0.7 nanometers.

8. 6. The container of claim 5, wherein the stored gaseous molecule diborane exhibits a reduced decomposition rate during storage at 22° C. compared to diborane stored on a microporous carbon adsorbent having a lower percentage of pores having a graphite interlayer spacing in the range of 0.4 to 0.8 nanometers.

9. 7. The container of claim 6, wherein the stored gaseous molecule diborane exhibits a reduced decomposition rate during storage at 22° C. compared to diborane stored on a microporous carbon adsorbent having a lower percentage of pores having a graphite interlayer spacing in the range of 0.4 to 0.8 nanometers.

10. 8. The container of claim 7, wherein the stored gaseous molecule diborane exhibits a reduced decomposition rate during storage at 22° C. compared to diborane stored on a microporous carbon adsorbent having a lower percentage of pores having graphite interlayer spacing in the range of 0.4 to 0.7 nanometers.

11. 1. A method for reversibly storing diborane in a container, comprising: a storage vessel comprising a microporous carbon adsorbent having slit pores between graphite layers having a graphite layer spacing that increase the activation energy required for decomposition of diborane relative to the activation energy for decomposition of unadsorbed gaseous diborane; adding diborane gas to the vessel so that the diborane is adsorbed onto the microporous carbon adsorbent; storing the adsorbed diborane in a container; A method comprising:

12. 12. The method of claim 11, wherein the vessel contains a concentration of diborane of at least 50 percent (atomic), based on the total amount of adsorbed and gaseous species within the vessel.

13. the activation energy being the sum of half the activation energy of reaction (i) plus the activation energy of reaction (ii), (i)B ２ H ６ →2BH ３ (ii) B ２ H ６ +BH ３ →B ３ H ９ The method of claim 11, wherein

14. 12. The method of claim 11, wherein the stored diborane undergoes reduced decomposition during storage as compared to the amount of decomposition of gaseous molecular diborane stored on a microporous carbon adsorbent having a lower percentage of pores having a graphite interlayer spacing in the range of 0.4 to 0.8 nanometers.

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