CUSIP No. 848565107

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                  SCHEDULE 13D

                                (AMENDMENT NO. 6)

                    UNDER THE SECURITIES EXCHANGE ACT OF 1934

                                Spire Corporation

                                (Name of Issuer)

                                  Common Stock

                         (Title of Class of Securities)

                                    848565107

                                 (CUSIP Number)

                            Joseph P. Bartlett, Esq.
                Greenberg Glusker Fields Claman & Machtinger LLP
                      1900 Avenue of the Stars, Suite 2100
                              Los Angeles, CA 90067
                                 (310) 201-7481

   (Name, Address and Telephone Number of Person Authorized to Receive Notices
                               and Communications)

                                February 19, 2008
             (Date of Event which Requires Filing of this Statement)

If the reporting person has previously filed a statement on Schedule 13G to
report the acquisition that is the subject of this Schedule 13D, and is filing
this schedule because of Sections 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g),
check the following box / /.

NOTE: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Section 240.13d-7(b) for
other parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).


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CUSIP No. 848565107

--------------------------------------------------------------------------------
(1)     Name of Reporting Person
        S.S. or I.R.S. Identification No. of Above Person

        David Gelbaum, Trustee, The Quercus Trust
--------------------------------------------------------------------------------
(2)     Check the Appropriate Box if a Member of a Group
        (See Instructions)                                              (A) /X/
                                                                        (B) / /
--------------------------------------------------------------------------------
(3)     SEC Use Only

--------------------------------------------------------------------------------
(4)     Source of Funds (See Instructions)

        PF
--------------------------------------------------------------------------------
(5)     Check if Disclosure of Legal Proceedings is Required
        Pursuant to Items 2(d) or 2(e)                                      / /

--------------------------------------------------------------------------------
(6)     Citizenship or Place of Organization

        U.S.
--------------------------------------------------------------------------------
                              (7)     Sole Voting Power
                                      -0-
                              --------------------------------------------------
Number of Shares              (8)     Shared Voting Power
Beneficially Owned                    1,022,056
by Each Reporting             --------------------------------------------------
Person With                   (9)     Sole Dispositive Power
                                      -0-
                              --------------------------------------------------
                              (10)    Shared Dispositive Power
                                      1,022,056
--------------------------------------------------------------------------------
(11)    Aggregate Amount Beneficially Owned by Each Reporting Person

        1,022,056
--------------------------------------------------------------------------------
(12)    Check if the Aggregate Amount in Row (11) Excludes Certain
        Shares (See Instructions)                                           / /
--------------------------------------------------------------------------------
(13)    Percent of Class Represented by Amount in Row (11)
        12.3%(1)
--------------------------------------------------------------------------------
(14)    Type of Reporting Person (See Instructions)
        IN
--------------------------------------------------------------------------------

-------------------------
(1)     Based on 8,305,788 shares of Common Stock outstanding, as reported in
        the Issuer's Quarterly Report on Form 10-Q for the quarterly period
        ended September 30, 2007.


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CUSIP No. 848565107

--------------------------------------------------------------------------------
(1)     Name of Reporting Person
        S.S. or I.R.S. Identification No. of Above Person

        Monica Chavez Gelbaum, Trustee, The Quercus Trust
--------------------------------------------------------------------------------
(2)     Check the Appropriate Box if a Member of a Group
        (See Instructions)                                              (A) /X/
                                                                        (B) / /
--------------------------------------------------------------------------------
(3)     SEC Use Only

--------------------------------------------------------------------------------
(4)     Source of Funds (See Instructions)

        PF
--------------------------------------------------------------------------------
(5)     Check if Disclosure of Legal Proceedings is Required
        Pursuant to Items 2(d) or 2(e)                                      / /

--------------------------------------------------------------------------------
(6)     Citizenship or Place of Organization

        U.S.
--------------------------------------------------------------------------------
                              (7)     Sole Voting Power
                                      -0-
                              --------------------------------------------------
Number of Shares              (8)     Shared Voting Power
Beneficially Owned                    1,022,056
by Each Reporting             --------------------------------------------------
Person With                   (9)     Sole Dispositive Power
                                      -0-
                              --------------------------------------------------
                              (10)    Shared Dispositive Power
                                      1,022,056
--------------------------------------------------------------------------------
(11)    Aggregate Amount Beneficially Owned by Each Reporting Person

        1,022,056
--------------------------------------------------------------------------------
(12)    Check if the Aggregate Amount in Row (11) Excludes Certain
        Shares (See Instructions)                                           / /
--------------------------------------------------------------------------------
(13)    Percent of Class Represented by Amount in Row (11)
        12.3%(1)
--------------------------------------------------------------------------------
(14)    Type of Reporting Person (See Instructions)
        IN
--------------------------------------------------------------------------------

-------------------------
(1)     Based on 8,305,788 shares of Common Stock outstanding, as reported in
        the Issuer's Quarterly Report on Form 10-Q for the quarterly period
        ended September 30, 2007.


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CUSIP No. 848565107

--------------------------------------------------------------------------------
(1)     Name of Reporting Person
        S.S. or I.R.S. Identification No. of Above Person

        The Quercus Trust
--------------------------------------------------------------------------------
(2)     Check the Appropriate Box if a Member of a Group
        (See Instructions)                                              (A) /X/
                                                                        (B) / /
--------------------------------------------------------------------------------
(3)     SEC Use Only

--------------------------------------------------------------------------------
(4)     Source of Funds (See Instructions)

        PF
--------------------------------------------------------------------------------
(5)     Check if Disclosure of Legal Proceedings is Required
        Pursuant to Items 2(d) or 2(e)                                      / /

--------------------------------------------------------------------------------
(6)     Citizenship or Place of Organization

        U.S.
--------------------------------------------------------------------------------
                              (7)     Sole Voting Power
                                      -0-
                              --------------------------------------------------
Number of Shares              (8)     Shared Voting Power
Beneficially Owned                    1,022,056
by Each Reporting             --------------------------------------------------
Person With                   (9)     Sole Dispositive Power
                                      -0-
                              --------------------------------------------------
                              (10)    Shared Dispositive Power
                                      1,022,056
--------------------------------------------------------------------------------
(11)    Aggregate Amount Beneficially Owned by Each Reporting Person

        1,022,056
--------------------------------------------------------------------------------
(12)    Check if the Aggregate Amount in Row (11) Excludes Certain
        Shares (See Instructions)                                           / /
--------------------------------------------------------------------------------
(13)    Percent of Class Represented by Amount in Row (11)
        12.3%(1)
--------------------------------------------------------------------------------
(14)    Type of Reporting Person (See Instructions)
        OO
--------------------------------------------------------------------------------

-------------------------
(1)     Based on 8,305,788 shares of Common Stock outstanding, as reported in
        the Issuer's Quarterly Report on Form 10-Q for the quarterly period
        ended September 30, 2007.


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CUSIP No. 848565107

Item 1.

        This Amendment No. 6 to Schedule 13D (this "Amendment No. 6") amends and
restates, where indicated, the statement on Schedule 13D relating to the Common
Stock of the Issuer filed by The Quercus Trust, David Gelbaum and Monica Chavez
Gelbaum (the "reporting persons") with the Securities and Exchange Commission on
August 31, 2007 (the "Initial Schedule 13D"), Amendment No. 1 to Schedule 13D
filed on September 28, 2007, Amendment No. 2 to Schedule 13D filed on October
16, 2007, Amendment No. 3 to Schedule 13D filed on November 20, 2007, Amendment
No. 4 to Schedule 13D filed on December 14, 2007 and Amendment No. 5 to Schedule
13D filed on February 4, 2008. Capitalized terms used in this Amendment No. 6
but not otherwise defined herein have the meanings given to them in the Initial
Schedule 13D or prior amendments thereto.

        This Amendment No. 6 is being made to disclose the acquisition of
additional shares (the "Shares") of Common Stock of the Issuer. Except as
otherwise set forth herein, this Amendment No. 6 does not modify any of the
information previously reported by the reporting persons in the Initial Schedule
13D or prior amendments thereto.

Item 5. Interest in Securities of the Issuer

        (a) As of the date of this Amendment No. 6, each reporting person
beneficially owns 1,022,056 shares of Common Stock, which are held of record by
the Trust.

        (b) Each of David Gelbaum and Monica Chavez Gelbaum, acting alone, has
the power to exercise voting and investment control over the shares of Common
Stock owned by the Trust.

        (c) Since February 4, 2008, the Trust has purchased shares of Common
Stock in brokered transactions as follows:

               Date            Number of Shares          Price Per Share
               ----            ----------------          ---------------
             2/4/2008               15,847                  $ 19.7972
             2/7/2008                4,100                  $ 17.9783
             2/8/2008                8,450                  $ 17.7486
            2/11/2008               15,000                  $ 17.5053
            2/12/2008                8,600                  $ 17.9565
            2/13/2008               10,200                  $ 19.0458
            2/14/2008               10,500                  $ 18.9760
            2/15/2008                8,000                  $ 17.8943
            2/19/2008                6,600                  $ 17.6130
            2/20/2008                8,546                  $ 17.2383
            2/21/2008                5,017                  $ 16.9703

        (d) Not applicable.

        (e) Not applicable.


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CUSIP No. 848565107


Item 6. Contracts, Arrangements, Understandings or Relationships With
        Respect to Securities of the Issuer

        Pursuant to the Power of Attorney filed as Exhibit "B" to Amendment No.
1 to Schedule 13D filed on August 24, 2007 with respect to the issuer Emcore
Corp., David Gelbaum has been appointed as Monica Chavez Gelbaum's
Attorney-In-Fact.

Item 7. Material to Be Filed as Exhibits

        Exhibit A: Agreement Regarding Joint Filing of Amendment No. 6 to
                   Schedule 13D.



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CUSIP No. 848565107


SIGNATURE

        After reasonable inquiry and to the best of its knowledge and belief,
each of the undersigned certifies that the information set forth in this
statement is true, complete and correct and agrees that this statement may be
filed jointly with the other undersigned parties.


Dated: February 25, 2008          /s/ David Gelbaum
                                  ----------------------------------------------
                                  David Gelbaum, Co-Trustee of The Quercus Trust



                                  /s/ David Gelbaum, as Attorney-In-Fact for
                                      Monica Chavez Gelbaum
                                  ----------------------------------------------
                                  Monica Chavez Gelbaum, Co-Trustee of The
                                  Quercus Trust



                                  /s/ David Gelbaum
                                  ----------------------------------------------
                                  The Quercus Trust, David Gelbaum, Co-Trustee
                                  of The Quercus Trust


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CUSIP No. 848565107


                                    EXHIBIT A

       AGREEMENT REGARDING JOINT FILING OF AMENDMENT NO. 6 TO SCHEDULE 13D
       -------------------------------------------------------------------



        The undersigned agree that the Amendment No. 6 to Schedule 13D with
respect to the Common Stock of Spire Corporation is a joint filing being made on
their behalf.


Dated: February 25, 2008          /s/ David Gelbaum
                                  ----------------------------------------------
                                  David Gelbaum, Co-Trustee of The Quercus Trust



                                  /s/ David Gelbaum, as Attorney-In-Fact for
                                      Monica Chavez Gelbaum
                                  ----------------------------------------------
                                  Monica Chavez Gelbaum, Co-Trustee of The
                                  Quercus Trust



                                  /s/ David Gelbaum
                                  ----------------------------------------------
                                  The Quercus Trust, David Gelbaum, Co-Trustee
                                  of The Quercus Trust


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